diff --git a/src/generators/Generator.ts b/src/generators/Generator.ts
index 1f48424c95..35bb2e9859 100644
--- a/src/generators/Generator.ts
+++ b/src/generators/Generator.ts
@@ -626,6 +626,10 @@ export default class Generator {
 					addDeclaration('store', templateProperties.store.value);
 				}
 
+				if (templateProperties.immutable) {
+					addDeclaration('immutable', templateProperties.immutable.value);
+				}
+
 				if (templateProperties.tag) {
 					this.tag = templateProperties.tag.value.value;
 				}
diff --git a/src/generators/dom/index.ts b/src/generators/dom/index.ts
index acf161642d..c1a23784b0 100644
--- a/src/generators/dom/index.ts
+++ b/src/generators/dom/index.ts
@@ -207,8 +207,8 @@ export default function dom(
 		${options.dev && `this._debugName = '${debugName}';`}
 		${options.dev && !generator.customElement &&
 			`if (!options || (!options.target && !options.root)) throw new Error("'target' is a required option");`}
+		${templateProperties.immutable && `if (!('immutable' in options)) options = assign({ immutable: %immutable }, options);`}
 		@init(this, options);
-		this._differs = @differs;
 		${templateProperties.store && `this.store = %store();`}
 		${generator.usesRefs && `this.refs = {};`}
 		this._state = @assign(${initialState.join(', ')});
@@ -376,7 +376,6 @@ export default function dom(
 			if (sigil === '@') {
 				if (name in shared) {
 					if (options.dev && `${name}Dev` in shared) name = `${name}Dev`;
-					else if (options.immutable && `${name}Immutable` in shared) name = `${name}Immutable`;
 					usedHelpers.add(name);
 				}
 
diff --git a/src/interfaces.ts b/src/interfaces.ts
index 82de8cd047..9773d330d3 100644
--- a/src/interfaces.ts
+++ b/src/interfaces.ts
@@ -52,7 +52,6 @@ export interface CompileOptions {
 	cssOutputFilename?: string;
 
 	dev?: boolean;
-	immutable?: boolean;
 	shared?: boolean | string;
 	cascade?: boolean;
 	hydratable?: boolean;
diff --git a/src/shared/index.js b/src/shared/index.js
index 0005569532..8506a5ed56 100644
--- a/src/shared/index.js
+++ b/src/shared/index.js
@@ -76,6 +76,8 @@ export function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 export function observe(key, callback, options) {
diff --git a/src/validate/js/propValidators/immutable.ts b/src/validate/js/propValidators/immutable.ts
new file mode 100644
index 0000000000..20e475340d
--- /dev/null
+++ b/src/validate/js/propValidators/immutable.ts
@@ -0,0 +1,11 @@
+import { Validator } from '../../';
+import { Node } from '../../../interfaces';
+
+export default function tag(validator: Validator, prop: Node) {
+	if (prop.value.type !== 'Literal' || typeof prop.value.value !== 'boolean') {
+		validator.error(
+			`'immutable' must be a boolean literal`,
+			prop.value.start
+		);
+	}
+}
diff --git a/src/validate/js/propValidators/index.ts b/src/validate/js/propValidators/index.ts
index 942c757601..05819b0837 100644
--- a/src/validate/js/propValidators/index.ts
+++ b/src/validate/js/propValidators/index.ts
@@ -15,6 +15,7 @@ import tag from './tag';
 import transitions from './transitions';
 import setup from './setup';
 import store from './store';
+import immutable from './immutable';
 
 export default {
 	data,
@@ -34,4 +35,5 @@ export default {
 	transitions,
 	setup,
 	store,
+	immutable,
 };
diff --git a/test/js/samples/collapses-text-around-comments/expected-bundle.js b/test/js/samples/collapses-text-around-comments/expected-bundle.js
index ba89e7777b..15e441a2b3 100644
--- a/test/js/samples/collapses-text-around-comments/expected-bundle.js
+++ b/test/js/samples/collapses-text-around-comments/expected-bundle.js
@@ -55,6 +55,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -98,6 +102,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -243,7 +249,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign(data(), options.data);
 
 	if (!document.getElementById("svelte-2794052100-style")) add_css();
diff --git a/test/js/samples/collapses-text-around-comments/expected.js b/test/js/samples/collapses-text-around-comments/expected.js
index a76fb36edf..aea4721e36 100644
--- a/test/js/samples/collapses-text-around-comments/expected.js
+++ b/test/js/samples/collapses-text-around-comments/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { appendNode, assign, createElement, createText, detachNode, differs, init, insertNode, noop, proto, setAttribute } from "svelte/shared.js";
+import { appendNode, assign, createElement, createText, detachNode, init, insertNode, noop, proto, setAttribute } from "svelte/shared.js";
 
 function data() {
 	return { foo: 42 }
@@ -51,7 +51,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign(data(), options.data);
 
 	if (!document.getElementById("svelte-2794052100-style")) add_css();
diff --git a/test/js/samples/computed-collapsed-if-immutable/expected-bundle.js b/test/js/samples/component-static-immutable/expected-bundle.js
similarity index 80%
rename from test/js/samples/computed-collapsed-if-immutable/expected-bundle.js
rename to test/js/samples/component-static-immutable/expected-bundle.js
index 509aa9328f..580ce5287b 100644
--- a/test/js/samples/computed-collapsed-if-immutable/expected-bundle.js
+++ b/test/js/samples/component-static-immutable/expected-bundle.js
@@ -27,6 +27,10 @@ function destroy(detach) {
 	this._fragment = this._state = null;
 }
 
+function differs(a, b) {
+	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
+}
+
 function differsImmutable(a, b) {
 	return a != a ? b == b : a !== b;
 }
@@ -74,6 +78,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -169,50 +175,63 @@ var proto = {
 };
 
 /* generated by Svelte vX.Y.Z */
-function a(x) {
-	return x * 2;
-}
+var Nested = window.Nested;
 
-function b(x) {
-	return x * 3;
-}
+var immutable = true;
 
 function create_main_fragment(state, component) {
 
+	var nested = new Nested({
+		root: component.root,
+		data: { foo: "bar" }
+	});
+
 	return {
-		c: noop,
+		c: function create() {
+			nested._fragment.c();
+		},
 
-		m: noop,
+		m: function mount(target, anchor) {
+			nested._mount(target, anchor);
+		},
 
 		p: noop,
 
-		u: noop,
+		u: function unmount() {
+			nested._unmount();
+		},
 
-		d: noop
+		d: function destroy$$1() {
+			nested.destroy(false);
+		}
 	};
 }
 
 function SvelteComponent(options) {
+	if (!('immutable' in options)) options = assign({ immutable: immutable }, options);
 	init(this, options);
-	this._differs = differsImmutable;
 	this._state = assign({}, options.data);
-	this._recompute({ x: 1 }, this._state);
+
+	if (!options.root) {
+		this._oncreate = [];
+		this._beforecreate = [];
+		this._aftercreate = [];
+	}
 
 	this._fragment = create_main_fragment(this._state, this);
 
 	if (options.target) {
 		this._fragment.c();
 		this._fragment.m(options.target, options.anchor || null);
+
+		this._lock = true;
+		callAll(this._beforecreate);
+		callAll(this._oncreate);
+		callAll(this._aftercreate);
+		this._lock = false;
 	}
 }
 
 assign(SvelteComponent.prototype, proto);
 
-SvelteComponent.prototype._recompute = function _recompute(changed, state) {
-	if (changed.x) {
-		if (this._differs(state.a, (state.a = a(state.x)))) changed.a = true;
-		if (this._differs(state.b, (state.b = b(state.x)))) changed.b = true;
-	}
-};
-
 export default SvelteComponent;
diff --git a/test/js/samples/component-static-immutable/expected.js b/test/js/samples/component-static-immutable/expected.js
new file mode 100644
index 0000000000..57ce7c1a85
--- /dev/null
+++ b/test/js/samples/component-static-immutable/expected.js
@@ -0,0 +1,62 @@
+/* generated by Svelte vX.Y.Z */
+import { assign, callAll, init, noop, proto } from "svelte/shared.js";
+
+var Nested = window.Nested;
+
+var immutable = true;
+
+function create_main_fragment(state, component) {
+
+	var nested = new Nested({
+		root: component.root,
+		data: { foo: "bar" }
+	});
+
+	return {
+		c: function create() {
+			nested._fragment.c();
+		},
+
+		m: function mount(target, anchor) {
+			nested._mount(target, anchor);
+		},
+
+		p: noop,
+
+		u: function unmount() {
+			nested._unmount();
+		},
+
+		d: function destroy() {
+			nested.destroy(false);
+		}
+	};
+}
+
+function SvelteComponent(options) {
+	if (!('immutable' in options)) options = assign({ immutable: immutable }, options);
+	init(this, options);
+	this._state = assign({}, options.data);
+
+	if (!options.root) {
+		this._oncreate = [];
+		this._beforecreate = [];
+		this._aftercreate = [];
+	}
+
+	this._fragment = create_main_fragment(this._state, this);
+
+	if (options.target) {
+		this._fragment.c();
+		this._fragment.m(options.target, options.anchor || null);
+
+		this._lock = true;
+		callAll(this._beforecreate);
+		callAll(this._oncreate);
+		callAll(this._aftercreate);
+		this._lock = false;
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+export default SvelteComponent;
\ No newline at end of file
diff --git a/test/js/samples/component-static-immutable/input.html b/test/js/samples/component-static-immutable/input.html
new file mode 100644
index 0000000000..df6c82ea81
--- /dev/null
+++ b/test/js/samples/component-static-immutable/input.html
@@ -0,0 +1,10 @@
+<Nested foo='bar'/>
+
+<script>
+	export default {
+		immutable: true,
+		components: {
+			Nested: window.Nested
+		}
+	};
+</script>
\ No newline at end of file
diff --git a/test/js/samples/component-static/expected-bundle.js b/test/js/samples/component-static/expected-bundle.js
index b28b38ddb6..161fc25d9d 100644
--- a/test/js/samples/component-static/expected-bundle.js
+++ b/test/js/samples/component-static/expected-bundle.js
@@ -31,6 +31,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -74,6 +78,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -201,7 +207,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	if (!options.root) {
diff --git a/test/js/samples/component-static/expected.js b/test/js/samples/component-static/expected.js
index de06c6fb2d..d75cce1253 100644
--- a/test/js/samples/component-static/expected.js
+++ b/test/js/samples/component-static/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, callAll, differs, init, noop, proto } from "svelte/shared.js";
+import { assign, callAll, init, noop, proto } from "svelte/shared.js";
 
 var Nested = window.Nested;
 
@@ -33,7 +33,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	if (!options.root) {
diff --git a/test/js/samples/computed-collapsed-if-immutable/_config.js b/test/js/samples/computed-collapsed-if-immutable/_config.js
deleted file mode 100644
index 06713941e0..0000000000
--- a/test/js/samples/computed-collapsed-if-immutable/_config.js
+++ /dev/null
@@ -1,5 +0,0 @@
-export default {
-	options: {
-		immutable: true
-	}
-};
\ No newline at end of file
diff --git a/test/js/samples/computed-collapsed-if-immutable/expected.js b/test/js/samples/computed-collapsed-if-immutable/expected.js
deleted file mode 100644
index b5beba1695..0000000000
--- a/test/js/samples/computed-collapsed-if-immutable/expected.js
+++ /dev/null
@@ -1,49 +0,0 @@
-/* generated by Svelte vX.Y.Z */
-import { assign, differsImmutable, init, noop, proto } from "svelte/shared.js";
-
-function a(x) {
-	return x * 2;
-}
-
-function b(x) {
-	return x * 3;
-}
-
-function create_main_fragment(state, component) {
-
-	return {
-		c: noop,
-
-		m: noop,
-
-		p: noop,
-
-		u: noop,
-
-		d: noop
-	};
-}
-
-function SvelteComponent(options) {
-	init(this, options);
-	this._differs = differsImmutable;
-	this._state = assign({}, options.data);
-	this._recompute({ x: 1 }, this._state);
-
-	this._fragment = create_main_fragment(this._state, this);
-
-	if (options.target) {
-		this._fragment.c();
-		this._fragment.m(options.target, options.anchor || null);
-	}
-}
-
-assign(SvelteComponent.prototype, proto);
-
-SvelteComponent.prototype._recompute = function _recompute(changed, state) {
-	if (changed.x) {
-		if (this._differs(state.a, (state.a = a(state.x)))) changed.a = true;
-		if (this._differs(state.b, (state.b = b(state.x)))) changed.b = true;
-	}
-}
-export default SvelteComponent;
\ No newline at end of file
diff --git a/test/js/samples/computed-collapsed-if-immutable/input.html b/test/js/samples/computed-collapsed-if-immutable/input.html
deleted file mode 100644
index a68513b860..0000000000
--- a/test/js/samples/computed-collapsed-if-immutable/input.html
+++ /dev/null
@@ -1,8 +0,0 @@
-<script>
-	export default {
-		computed: {
-			a: x => x * 2,
-			b: x => x * 3
-		}
-	};
-</script>
\ No newline at end of file
diff --git a/test/js/samples/computed-collapsed-if/expected-bundle.js b/test/js/samples/computed-collapsed-if/expected-bundle.js
index 475b5d3491..41cf402472 100644
--- a/test/js/samples/computed-collapsed-if/expected-bundle.js
+++ b/test/js/samples/computed-collapsed-if/expected-bundle.js
@@ -31,6 +31,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -74,6 +78,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -194,7 +200,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 	this._recompute({ x: 1 }, this._state);
 
diff --git a/test/js/samples/computed-collapsed-if/expected.js b/test/js/samples/computed-collapsed-if/expected.js
index c0765a4115..085365f4c5 100644
--- a/test/js/samples/computed-collapsed-if/expected.js
+++ b/test/js/samples/computed-collapsed-if/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, differs, init, noop, proto } from "svelte/shared.js";
+import { assign, init, noop, proto } from "svelte/shared.js";
 
 function a(x) {
 	return x * 2;
@@ -26,7 +26,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 	this._recompute({ x: 1 }, this._state);
 
diff --git a/test/js/samples/css-media-query/expected-bundle.js b/test/js/samples/css-media-query/expected-bundle.js
index cfed183001..f70404e499 100644
--- a/test/js/samples/css-media-query/expected-bundle.js
+++ b/test/js/samples/css-media-query/expected-bundle.js
@@ -51,6 +51,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -94,6 +98,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -229,7 +235,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	if (!document.getElementById("svelte-3905933315-style")) add_css();
diff --git a/test/js/samples/css-media-query/expected.js b/test/js/samples/css-media-query/expected.js
index 61e78032e8..37afa6b42a 100644
--- a/test/js/samples/css-media-query/expected.js
+++ b/test/js/samples/css-media-query/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { appendNode, assign, createElement, detachNode, differs, init, insertNode, noop, proto, setAttribute } from "svelte/shared.js";
+import { appendNode, assign, createElement, detachNode, init, insertNode, noop, proto, setAttribute } from "svelte/shared.js";
 
 function encapsulateStyles(node) {
 	setAttribute(node, "svelte-3905933315", "");
@@ -41,7 +41,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	if (!document.getElementById("svelte-3905933315-style")) add_css();
diff --git a/test/js/samples/css-shadow-dom-keyframes/expected-bundle.js b/test/js/samples/css-shadow-dom-keyframes/expected-bundle.js
index 2684f5ddb7..216ad97fe2 100644
--- a/test/js/samples/css-shadow-dom-keyframes/expected-bundle.js
+++ b/test/js/samples/css-shadow-dom-keyframes/expected-bundle.js
@@ -43,6 +43,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -86,6 +90,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -209,7 +215,6 @@ class SvelteComponent extends HTMLElement {
 	constructor(options = {}) {
 		super();
 		init(this, options);
-		this._differs = differs;
 		this._state = assign({}, options.data);
 
 		this.attachShadow({ mode: 'open' });
diff --git a/test/js/samples/css-shadow-dom-keyframes/expected.js b/test/js/samples/css-shadow-dom-keyframes/expected.js
index de4528ff0e..496586e632 100644
--- a/test/js/samples/css-shadow-dom-keyframes/expected.js
+++ b/test/js/samples/css-shadow-dom-keyframes/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createElement, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { assign, createElement, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var div;
@@ -29,7 +29,6 @@ class SvelteComponent extends HTMLElement {
 	constructor(options = {}) {
 		super();
 		init(this, options);
-		this._differs = differs;
 		this._state = assign({}, options.data);
 
 		this.attachShadow({ mode: 'open' });
diff --git a/test/js/samples/deconflict-globals/expected-bundle.js b/test/js/samples/deconflict-globals/expected-bundle.js
index b3e979c0e9..7769b49deb 100644
--- a/test/js/samples/deconflict-globals/expected-bundle.js
+++ b/test/js/samples/deconflict-globals/expected-bundle.js
@@ -31,6 +31,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -74,6 +78,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -196,7 +202,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign(data_1(), options.data);
 
 	var _oncreate = oncreate.bind(this);
diff --git a/test/js/samples/deconflict-globals/expected.js b/test/js/samples/deconflict-globals/expected.js
index 95da7a1a0c..8730f4e3c3 100644
--- a/test/js/samples/deconflict-globals/expected.js
+++ b/test/js/samples/deconflict-globals/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, callAll, differs, init, noop, proto } from "svelte/shared.js";
+import { assign, callAll, init, noop, proto } from "svelte/shared.js";
 
 function data_1() {
 	return {
@@ -28,7 +28,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign(data_1(), options.data);
 
 	var _oncreate = oncreate.bind(this);
diff --git a/test/js/samples/do-use-dataset/expected-bundle.js b/test/js/samples/do-use-dataset/expected-bundle.js
index 8974c8a808..3b955df698 100644
--- a/test/js/samples/do-use-dataset/expected-bundle.js
+++ b/test/js/samples/do-use-dataset/expected-bundle.js
@@ -47,6 +47,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -90,6 +94,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -225,7 +231,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/do-use-dataset/expected.js b/test/js/samples/do-use-dataset/expected.js
index cbe6e9ac2b..1ae7417469 100644
--- a/test/js/samples/do-use-dataset/expected.js
+++ b/test/js/samples/do-use-dataset/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createElement, createText, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { assign, createElement, createText, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var div, text, div_1;
@@ -41,7 +41,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/dont-use-dataset-in-legacy/expected-bundle.js b/test/js/samples/dont-use-dataset-in-legacy/expected-bundle.js
index 9f546da356..15c19756cb 100644
--- a/test/js/samples/dont-use-dataset-in-legacy/expected-bundle.js
+++ b/test/js/samples/dont-use-dataset-in-legacy/expected-bundle.js
@@ -51,6 +51,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -94,6 +98,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -229,7 +235,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/dont-use-dataset-in-legacy/expected.js b/test/js/samples/dont-use-dataset-in-legacy/expected.js
index 989b1a47f8..03eef26ced 100644
--- a/test/js/samples/dont-use-dataset-in-legacy/expected.js
+++ b/test/js/samples/dont-use-dataset-in-legacy/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createElement, createText, detachNode, differs, init, insertNode, noop, proto, setAttribute } from "svelte/shared.js";
+import { assign, createElement, createText, detachNode, init, insertNode, noop, proto, setAttribute } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var div, text, div_1;
@@ -41,7 +41,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/dont-use-dataset-in-svg/expected-bundle.js b/test/js/samples/dont-use-dataset-in-svg/expected-bundle.js
index e6c5fee0c6..ee846b8fb4 100644
--- a/test/js/samples/dont-use-dataset-in-svg/expected-bundle.js
+++ b/test/js/samples/dont-use-dataset-in-svg/expected-bundle.js
@@ -51,6 +51,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -94,6 +98,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -227,7 +233,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/dont-use-dataset-in-svg/expected.js b/test/js/samples/dont-use-dataset-in-svg/expected.js
index f96da75975..b87f152298 100644
--- a/test/js/samples/dont-use-dataset-in-svg/expected.js
+++ b/test/js/samples/dont-use-dataset-in-svg/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { appendNode, assign, createSvgElement, detachNode, differs, init, insertNode, noop, proto, setAttribute } from "svelte/shared.js";
+import { appendNode, assign, createSvgElement, detachNode, init, insertNode, noop, proto, setAttribute } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var svg, g, g_1;
@@ -39,7 +39,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/each-block-changed-check/expected-bundle.js b/test/js/samples/each-block-changed-check/expected-bundle.js
index 428e9c739a..d717803108 100644
--- a/test/js/samples/each-block-changed-check/expected-bundle.js
+++ b/test/js/samples/each-block-changed-check/expected-bundle.js
@@ -63,6 +63,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -106,6 +110,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -341,7 +347,6 @@ function create_each_block(state, comments, comment, i, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/each-block-changed-check/expected.js b/test/js/samples/each-block-changed-check/expected.js
index c436550f07..29a57322e0 100644
--- a/test/js/samples/each-block-changed-check/expected.js
+++ b/test/js/samples/each-block-changed-check/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { appendNode, assign, createElement, createText, destroyEach, detachAfter, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { appendNode, assign, createElement, createText, destroyEach, detachAfter, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var text, p, text_1;
@@ -141,7 +141,6 @@ function create_each_block(state, comments, comment, i, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/event-handlers-custom/expected-bundle.js b/test/js/samples/event-handlers-custom/expected-bundle.js
index 819b653caa..dbda232f59 100644
--- a/test/js/samples/event-handlers-custom/expected-bundle.js
+++ b/test/js/samples/event-handlers-custom/expected-bundle.js
@@ -43,6 +43,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -86,6 +90,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -226,7 +232,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/event-handlers-custom/expected.js b/test/js/samples/event-handlers-custom/expected.js
index 1d5ae4b17e..f7862efb62 100644
--- a/test/js/samples/event-handlers-custom/expected.js
+++ b/test/js/samples/event-handlers-custom/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createElement, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { assign, createElement, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function foo( node, callback ) {
 	// code goes here
@@ -46,7 +46,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/head-no-whitespace/expected-bundle.js b/test/js/samples/head-no-whitespace/expected-bundle.js
index 398617dd13..c0ae2a8ba0 100644
--- a/test/js/samples/head-no-whitespace/expected-bundle.js
+++ b/test/js/samples/head-no-whitespace/expected-bundle.js
@@ -43,6 +43,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -86,6 +90,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -216,7 +222,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/head-no-whitespace/expected.js b/test/js/samples/head-no-whitespace/expected.js
index d9bee61c62..32a1a5da88 100644
--- a/test/js/samples/head-no-whitespace/expected.js
+++ b/test/js/samples/head-no-whitespace/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { appendNode, assign, createElement, detachNode, differs, init, noop, proto } from "svelte/shared.js";
+import { appendNode, assign, createElement, detachNode, init, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var meta, meta_1;
@@ -36,7 +36,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/if-block-no-update/expected-bundle.js b/test/js/samples/if-block-no-update/expected-bundle.js
index b3dc0c6b13..31d618922e 100644
--- a/test/js/samples/if-block-no-update/expected-bundle.js
+++ b/test/js/samples/if-block-no-update/expected-bundle.js
@@ -47,6 +47,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -90,6 +94,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -274,7 +280,6 @@ function select_block_type(state) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/if-block-no-update/expected.js b/test/js/samples/if-block-no-update/expected.js
index 59c54d1ad7..8f030e4e53 100644
--- a/test/js/samples/if-block-no-update/expected.js
+++ b/test/js/samples/if-block-no-update/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createComment, createElement, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { assign, createComment, createElement, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var if_block_anchor;
@@ -90,7 +90,6 @@ function select_block_type(state) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/if-block-simple/expected-bundle.js b/test/js/samples/if-block-simple/expected-bundle.js
index 9dac6d03a9..f36462efad 100644
--- a/test/js/samples/if-block-simple/expected-bundle.js
+++ b/test/js/samples/if-block-simple/expected-bundle.js
@@ -47,6 +47,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -90,6 +94,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -250,7 +256,6 @@ function create_if_block(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/if-block-simple/expected.js b/test/js/samples/if-block-simple/expected.js
index 667640451f..0b9fbece70 100644
--- a/test/js/samples/if-block-simple/expected.js
+++ b/test/js/samples/if-block-simple/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createComment, createElement, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { assign, createComment, createElement, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var if_block_anchor;
@@ -66,7 +66,6 @@ function create_if_block(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/inline-style-optimized-multiple/expected-bundle.js b/test/js/samples/inline-style-optimized-multiple/expected-bundle.js
index 8843db047b..57402a155a 100644
--- a/test/js/samples/inline-style-optimized-multiple/expected-bundle.js
+++ b/test/js/samples/inline-style-optimized-multiple/expected-bundle.js
@@ -47,6 +47,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -90,6 +94,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -223,7 +229,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/inline-style-optimized-multiple/expected.js b/test/js/samples/inline-style-optimized-multiple/expected.js
index 0b0aca132b..77173460e2 100644
--- a/test/js/samples/inline-style-optimized-multiple/expected.js
+++ b/test/js/samples/inline-style-optimized-multiple/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createElement, detachNode, differs, init, insertNode, noop, proto, setStyle } from "svelte/shared.js";
+import { assign, createElement, detachNode, init, insertNode, noop, proto, setStyle } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var div;
@@ -39,7 +39,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/inline-style-optimized-url/expected-bundle.js b/test/js/samples/inline-style-optimized-url/expected-bundle.js
index e88379a4e4..069cc003b7 100644
--- a/test/js/samples/inline-style-optimized-url/expected-bundle.js
+++ b/test/js/samples/inline-style-optimized-url/expected-bundle.js
@@ -47,6 +47,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -90,6 +94,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -218,7 +224,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/inline-style-optimized-url/expected.js b/test/js/samples/inline-style-optimized-url/expected.js
index 1d8d5c467a..bed00356f6 100644
--- a/test/js/samples/inline-style-optimized-url/expected.js
+++ b/test/js/samples/inline-style-optimized-url/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createElement, detachNode, differs, init, insertNode, noop, proto, setStyle } from "svelte/shared.js";
+import { assign, createElement, detachNode, init, insertNode, noop, proto, setStyle } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var div;
@@ -34,7 +34,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/inline-style-optimized/expected-bundle.js b/test/js/samples/inline-style-optimized/expected-bundle.js
index a1b8278e87..643017655d 100644
--- a/test/js/samples/inline-style-optimized/expected-bundle.js
+++ b/test/js/samples/inline-style-optimized/expected-bundle.js
@@ -47,6 +47,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -90,6 +94,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -218,7 +224,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/inline-style-optimized/expected.js b/test/js/samples/inline-style-optimized/expected.js
index 7f4f19248b..7f873e296c 100644
--- a/test/js/samples/inline-style-optimized/expected.js
+++ b/test/js/samples/inline-style-optimized/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createElement, detachNode, differs, init, insertNode, noop, proto, setStyle } from "svelte/shared.js";
+import { assign, createElement, detachNode, init, insertNode, noop, proto, setStyle } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var div;
@@ -34,7 +34,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/inline-style-unoptimized/expected-bundle.js b/test/js/samples/inline-style-unoptimized/expected-bundle.js
index 9db0da26fe..906bf21bb5 100644
--- a/test/js/samples/inline-style-unoptimized/expected-bundle.js
+++ b/test/js/samples/inline-style-unoptimized/expected-bundle.js
@@ -47,6 +47,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -90,6 +94,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -229,7 +235,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/inline-style-unoptimized/expected.js b/test/js/samples/inline-style-unoptimized/expected.js
index 0e53480fe8..4c4d38d2bf 100644
--- a/test/js/samples/inline-style-unoptimized/expected.js
+++ b/test/js/samples/inline-style-unoptimized/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createElement, createText, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { assign, createElement, createText, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var div, text, div_1, div_1_style_value;
@@ -45,7 +45,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/input-without-blowback-guard/expected-bundle.js b/test/js/samples/input-without-blowback-guard/expected-bundle.js
index fb3f125b00..a02405f10a 100644
--- a/test/js/samples/input-without-blowback-guard/expected-bundle.js
+++ b/test/js/samples/input-without-blowback-guard/expected-bundle.js
@@ -51,6 +51,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -94,6 +98,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -229,7 +235,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/input-without-blowback-guard/expected.js b/test/js/samples/input-without-blowback-guard/expected.js
index 9342b25ec9..03f27ab6d9 100644
--- a/test/js/samples/input-without-blowback-guard/expected.js
+++ b/test/js/samples/input-without-blowback-guard/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { addListener, assign, createElement, detachNode, differs, init, insertNode, proto, removeListener } from "svelte/shared.js";
+import { addListener, assign, createElement, detachNode, init, insertNode, proto, removeListener } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var input;
@@ -41,7 +41,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/legacy-input-type/expected-bundle.js b/test/js/samples/legacy-input-type/expected-bundle.js
index 8b6e2faa8f..b54727a24c 100644
--- a/test/js/samples/legacy-input-type/expected-bundle.js
+++ b/test/js/samples/legacy-input-type/expected-bundle.js
@@ -49,6 +49,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -92,6 +96,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -216,7 +222,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/legacy-input-type/expected.js b/test/js/samples/legacy-input-type/expected.js
index 22d71f036d..719f550044 100644
--- a/test/js/samples/legacy-input-type/expected.js
+++ b/test/js/samples/legacy-input-type/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, createElement, detachNode, differs, init, insertNode, noop, proto, setInputType } from "svelte/shared.js";
+import { assign, createElement, detachNode, init, insertNode, noop, proto, setInputType } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var input;
@@ -30,7 +30,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/legacy-quote-class/expected-bundle.js b/test/js/samples/legacy-quote-class/expected-bundle.js
index b4900a16b5..3177f32f16 100644
--- a/test/js/samples/legacy-quote-class/expected-bundle.js
+++ b/test/js/samples/legacy-quote-class/expected-bundle.js
@@ -66,6 +66,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -109,6 +113,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -241,7 +247,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/legacy-quote-class/expected.js b/test/js/samples/legacy-quote-class/expected.js
index c4421f91cd..0b49103c47 100644
--- a/test/js/samples/legacy-quote-class/expected.js
+++ b/test/js/samples/legacy-quote-class/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, children, claimElement, createElement, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { assign, children, claimElement, createElement, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var div;
@@ -38,7 +38,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/media-bindings/expected-bundle.js b/test/js/samples/media-bindings/expected-bundle.js
index 2eacb53f8c..7a258f8965 100644
--- a/test/js/samples/media-bindings/expected-bundle.js
+++ b/test/js/samples/media-bindings/expected-bundle.js
@@ -59,6 +59,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -102,6 +106,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -282,7 +288,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	if (!options.root) {
diff --git a/test/js/samples/media-bindings/expected.js b/test/js/samples/media-bindings/expected.js
index 503228ce06..ae80f288f6 100644
--- a/test/js/samples/media-bindings/expected.js
+++ b/test/js/samples/media-bindings/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { addListener, assign, callAll, createElement, detachNode, differs, init, insertNode, proto, removeListener, timeRangesToArray } from "svelte/shared.js";
+import { addListener, assign, callAll, createElement, detachNode, init, insertNode, proto, removeListener, timeRangesToArray } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var audio, audio_is_paused = true, audio_updating = false, audio_animationframe;
@@ -86,7 +86,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	if (!options.root) {
diff --git a/test/js/samples/non-imported-component/expected-bundle.js b/test/js/samples/non-imported-component/expected-bundle.js
index 9cba5b8bfb..2799a85ebe 100644
--- a/test/js/samples/non-imported-component/expected-bundle.js
+++ b/test/js/samples/non-imported-component/expected-bundle.js
@@ -45,6 +45,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -88,6 +92,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -224,7 +230,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	if (!options.root) {
diff --git a/test/js/samples/non-imported-component/expected.js b/test/js/samples/non-imported-component/expected.js
index c35b4f88a7..e7fc2c7255 100644
--- a/test/js/samples/non-imported-component/expected.js
+++ b/test/js/samples/non-imported-component/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, callAll, createText, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { assign, callAll, createText, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 import Imported from 'Imported.html';
 
 
@@ -45,7 +45,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	if (!options.root) {
diff --git a/test/js/samples/onrender-onteardown-rewritten/expected-bundle.js b/test/js/samples/onrender-onteardown-rewritten/expected-bundle.js
index 26f52231fc..049ba0d86a 100644
--- a/test/js/samples/onrender-onteardown-rewritten/expected-bundle.js
+++ b/test/js/samples/onrender-onteardown-rewritten/expected-bundle.js
@@ -31,6 +31,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -74,6 +78,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -190,7 +196,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._handlers.destroy = [ondestroy];
diff --git a/test/js/samples/onrender-onteardown-rewritten/expected.js b/test/js/samples/onrender-onteardown-rewritten/expected.js
index 02203f83c0..51763c0b00 100644
--- a/test/js/samples/onrender-onteardown-rewritten/expected.js
+++ b/test/js/samples/onrender-onteardown-rewritten/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, callAll, differs, init, noop, proto } from "svelte/shared.js";
+import { assign, callAll, init, noop, proto } from "svelte/shared.js";
 
 function oncreate() {};
 
@@ -22,7 +22,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._handlers.destroy = [ondestroy];
diff --git a/test/js/samples/setup-method/expected-bundle.js b/test/js/samples/setup-method/expected-bundle.js
index 103bf174ac..388bb495bc 100644
--- a/test/js/samples/setup-method/expected-bundle.js
+++ b/test/js/samples/setup-method/expected-bundle.js
@@ -31,6 +31,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -74,6 +78,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -202,7 +208,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/setup-method/expected.js b/test/js/samples/setup-method/expected.js
index 5b306a12e7..092a32ed3b 100644
--- a/test/js/samples/setup-method/expected.js
+++ b/test/js/samples/setup-method/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, differs, init, noop, proto } from "svelte/shared.js";
+import { assign, init, noop, proto } from "svelte/shared.js";
 
 var methods = {
 	foo ( bar ) {
@@ -34,7 +34,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/svg-title/expected-bundle.js b/test/js/samples/svg-title/expected-bundle.js
index 2050f6dcfe..46880a584c 100644
--- a/test/js/samples/svg-title/expected-bundle.js
+++ b/test/js/samples/svg-title/expected-bundle.js
@@ -51,6 +51,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -94,6 +98,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -217,7 +223,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/svg-title/expected.js b/test/js/samples/svg-title/expected.js
index 6c5d08ca00..39ccf227c0 100644
--- a/test/js/samples/svg-title/expected.js
+++ b/test/js/samples/svg-title/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { appendNode, assign, createSvgElement, createText, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { appendNode, assign, createSvgElement, createText, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var svg, title, text;
@@ -29,7 +29,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/title/expected-bundle.js b/test/js/samples/title/expected-bundle.js
index 2fcc0b6197..4e70625f70 100644
--- a/test/js/samples/title/expected-bundle.js
+++ b/test/js/samples/title/expected-bundle.js
@@ -31,6 +31,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -74,6 +78,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -193,7 +199,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/title/expected.js b/test/js/samples/title/expected.js
index e15441fbdc..6aa903d25e 100644
--- a/test/js/samples/title/expected.js
+++ b/test/js/samples/title/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { assign, differs, init, noop, proto } from "svelte/shared.js";
+import { assign, init, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var title_value;
@@ -25,7 +25,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/use-elements-as-anchors/expected-bundle.js b/test/js/samples/use-elements-as-anchors/expected-bundle.js
index e22e431d53..2045954b41 100644
--- a/test/js/samples/use-elements-as-anchors/expected-bundle.js
+++ b/test/js/samples/use-elements-as-anchors/expected-bundle.js
@@ -55,6 +55,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -98,6 +102,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -440,7 +446,6 @@ function create_if_block_4(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/use-elements-as-anchors/expected.js b/test/js/samples/use-elements-as-anchors/expected.js
index 0b45ca8679..d2609c45b0 100644
--- a/test/js/samples/use-elements-as-anchors/expected.js
+++ b/test/js/samples/use-elements-as-anchors/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { appendNode, assign, createComment, createElement, createText, detachNode, differs, init, insertNode, noop, proto } from "svelte/shared.js";
+import { appendNode, assign, createComment, createElement, createText, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var div, text, p, text_2, text_3, text_4, p_1, text_6, text_8, if_block_4_anchor;
@@ -248,7 +248,6 @@ function create_if_block_4(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 
 	this._fragment = create_main_fragment(this._state, this);
diff --git a/test/js/samples/window-binding-scroll/expected-bundle.js b/test/js/samples/window-binding-scroll/expected-bundle.js
index 97231f4bb6..b0014988b7 100644
--- a/test/js/samples/window-binding-scroll/expected-bundle.js
+++ b/test/js/samples/window-binding-scroll/expected-bundle.js
@@ -51,6 +51,10 @@ function differs(a, b) {
 	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
 }
 
+function differsImmutable(a, b) {
+	return a != a ? b == b : a !== b;
+}
+
 function dispatchObservers(component, group, changed, newState, oldState) {
 	for (var key in group) {
 		if (!changed[key]) continue;
@@ -94,6 +98,8 @@ function init(component, options) {
 	component.options = options;
 	component.root = options.root || component;
 	component.store = component.root.store || options.store;
+	var immutable = options.immutable !== undefined ? options.immutable : component.root.options.immutable;
+	component._differs = immutable ? differsImmutable : differs;
 }
 
 function observe(key, callback, options) {
@@ -241,7 +247,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 	this._state.y = window.scrollY;
 
diff --git a/test/js/samples/window-binding-scroll/expected.js b/test/js/samples/window-binding-scroll/expected.js
index 55bc0eb53a..70eae003d7 100644
--- a/test/js/samples/window-binding-scroll/expected.js
+++ b/test/js/samples/window-binding-scroll/expected.js
@@ -1,5 +1,5 @@
 /* generated by Svelte vX.Y.Z */
-import { appendNode, assign, createElement, createText, detachNode, differs, init, insertNode, proto } from "svelte/shared.js";
+import { appendNode, assign, createElement, createText, detachNode, init, insertNode, proto } from "svelte/shared.js";
 
 function create_main_fragment(state, component) {
 	var window_updating = false, clear_window_updating = function() { window_updating = false; }, window_updating_timeout, p, text, text_1;
@@ -53,7 +53,6 @@ function create_main_fragment(state, component) {
 
 function SvelteComponent(options) {
 	init(this, options);
-	this._differs = differs;
 	this._state = assign({}, options.data);
 	this._state.y = window.scrollY;