diff --git a/test/js/samples/debug-hoisted/expected.js b/test/js/samples/debug-hoisted/expected.js
index c77168ef4f..190ff12c50 100644
--- a/test/js/samples/debug-hoisted/expected.js
+++ b/test/js/samples/debug-hoisted/expected.js
@@ -50,6 +50,12 @@ function create_fragment(ctx) {
 function instance($$self, $$props, $$invalidate) {
 	let obj = { x: 5 };
 	let kobzol = 5;
+	const writable_props = [];
+
+	Object.keys($$props).forEach(key => {
+		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
+	});
+
 	$$self.$capture_state = () => ({ obj, kobzol });
 
 	$$self.$inject_state = $$props => {
diff --git a/test/js/samples/loop-protect/expected.js b/test/js/samples/loop-protect/expected.js
index 127addf1d1..25cd2d9c7b 100644
--- a/test/js/samples/loop-protect/expected.js
+++ b/test/js/samples/loop-protect/expected.js
@@ -6,6 +6,7 @@ import {
 	detach_dev,
 	dispatch_dev,
 	element,
+	globals,
 	init,
 	insert_dev,
 	loop_guard,
@@ -13,6 +14,7 @@ import {
 	safe_not_equal
 } from "svelte/internal";
 
+const { console: console_1 } = globals;
 const file = undefined;
 
 function create_fragment(ctx) {
@@ -102,6 +104,12 @@ function instance($$self, $$props, $$invalidate) {
 		} while (true);
 	}
 
+	const writable_props = [];
+
+	Object.keys($$props).forEach(key => {
+		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console_1.warn(`<Component> was created with unknown prop '${key}'`);
+	});
+
 	function div_binding($$value) {
 		binding_callbacks[$$value ? "unshift" : "push"](() => {
 			$$invalidate(0, node = $$value);