diff --git a/packages/svelte/src/internal/client/dom/blocks/if.js b/packages/svelte/src/internal/client/dom/blocks/if.js
index 164cd7ea60..d6001bab86 100644
--- a/packages/svelte/src/internal/client/dom/blocks/if.js
+++ b/packages/svelte/src/internal/client/dom/blocks/if.js
@@ -29,10 +29,8 @@ export function if_block(anchor_node, condition_fn, consequent_fn, alternate_fn)
 	/** @type {boolean | null} */
 	let condition = null;
 
-	let mounted = false;
-
 	render_effect(() => {
-		if (condition === (condition = condition_fn())) return;
+		if (condition === (condition = !!condition_fn())) return;
 
 		if (hydrating) {
 			const comment_text = /** @type {Comment} */ (current_hydration_fragment?.[0])?.data;
@@ -56,7 +54,7 @@ export function if_block(anchor_node, condition_fn, consequent_fn, alternate_fn)
 			if (consequent_effect) {
 				resume_effect(consequent_effect);
 			} else {
-				consequent_effect = render_effect(() => consequent_fn(anchor_node));
+				consequent_effect = render_effect(() => consequent_fn(anchor_node), {}, true);
 			}
 
 			if (alternate_effect) {
@@ -68,7 +66,7 @@ export function if_block(anchor_node, condition_fn, consequent_fn, alternate_fn)
 			if (alternate_effect) {
 				resume_effect(alternate_effect);
 			} else {
-				alternate_effect = alternate_fn && render_effect(() => alternate_fn(anchor_node));
+				alternate_effect = alternate_fn && render_effect(() => alternate_fn(anchor_node), {}, true);
 			}
 
 			if (consequent_effect) {
@@ -78,6 +76,4 @@ export function if_block(anchor_node, condition_fn, consequent_fn, alternate_fn)
 			}
 		}
 	});
-
-	mounted = true;
 }
diff --git a/packages/svelte/src/internal/client/reactivity/computations.js b/packages/svelte/src/internal/client/reactivity/computations.js
index 30ec4fcb69..cec1ce6799 100644
--- a/packages/svelte/src/internal/client/reactivity/computations.js
+++ b/packages/svelte/src/internal/client/reactivity/computations.js
@@ -19,8 +19,10 @@ import {
 	DERIVED,
 	UNOWNED,
 	CLEAN,
-	UNINITIALIZED
+	UNINITIALIZED,
+	INERT
 } from '../constants.js';
+import { noop } from '../../common.js';
 
 /**
  * @template V
@@ -263,8 +265,20 @@ export function derived_safe_equal(fn) {
  * @param {() => void} done
  */
 export function pause_effect(effect, done) {
-	// TODO pause children
-	remove(effect.dom);
+	if (effect.r) {
+		for (const child of effect.r) {
+			pause_effect(child, noop);
+		}
+	}
+
+	effect.f |= INERT;
+
+	// TODO distinguish between 'block effects' (?) which own their own DOM
+	// and other render effects
+	if (effect.dom) {
+		remove(effect.dom);
+	}
+
 	done(); // TODO defer until transitions have completed
 }