diff --git a/packages/svelte/.gitignore b/packages/svelte/.gitignore
index e4925570e5..8b3d7652a1 100644
--- a/packages/svelte/.gitignore
+++ b/packages/svelte/.gitignore
@@ -11,3 +11,5 @@
 /motion.d.ts
 /store.d.ts
 /transition.d.ts
+
+/scripts/_bundle.js
diff --git a/packages/svelte/scripts/check-treeshakeability.js b/packages/svelte/scripts/check-treeshakeability.js
index 21f33ab6f0..9ded247b2b 100644
--- a/packages/svelte/scripts/check-treeshakeability.js
+++ b/packages/svelte/scripts/check-treeshakeability.js
@@ -74,7 +74,7 @@ for (const key in pkg.exports) {
 }
 
 const client_main = path.resolve(pkg.exports['.'].browser);
-const without_hydration = await bundle_code(
+const bundle = await bundle_code(
 	// Use all features which contain hydration code to ensure it's treeshakeable
 	compile(
 		`
@@ -109,15 +109,17 @@ const without_hydration = await bundle_code(
 	).js.code
 );
 
-if (!without_hydration.includes('current_hydration_fragment')) {
+if (!bundle.includes('current_hydration_fragment')) {
 	// eslint-disable-next-line no-console
 	console.error(`✅ Hydration code treeshakeable`);
 } else {
 	// eslint-disable-next-line no-console
-	console.error(without_hydration);
+	console.error(bundle);
 	// eslint-disable-next-line no-console
 	console.error(`❌ Hydration code not treeshakeable`);
 	failed = true;
+
+	fs.writeFileSync('scripts/_bundle.js', bundle);
 }
 
 // eslint-disable-next-line no-console
diff --git a/packages/svelte/src/internal/client/dom/blocks/if.js b/packages/svelte/src/internal/client/dom/blocks/if.js
index 8c35d98530..da1c04070e 100644
--- a/packages/svelte/src/internal/client/dom/blocks/if.js
+++ b/packages/svelte/src/internal/client/dom/blocks/if.js
@@ -41,9 +41,6 @@ export function if_block(anchor_node, condition_fn, consequent_fn, alternate_fn,
 
 	hydrate_block_anchor(anchor_node);
 
-	/** Whether or not there was a hydration mismatch. Needs to be a `let` or else it isn't treeshaken out */
-	let mismatch = false;
-
 	/** @type {null | import('#client').TemplateNode | Array<import('#client').TemplateNode>} */
 	let consequent_dom = null;
 
@@ -62,6 +59,9 @@ export function if_block(anchor_node, condition_fn, consequent_fn, alternate_fn,
 	const if_effect = render_effect(() => {
 		if (condition === (condition = !!condition_fn())) return;
 
+		/** Whether or not there was a hydration mismatch. Needs to be a `let` or else it isn't treeshaken out */
+		let mismatch = false;
+
 		if (hydrating) {
 			const comment_text = /** @type {Comment} */ (current_hydration_fragment?.[0])?.data;
 
@@ -154,8 +154,6 @@ export function if_block(anchor_node, condition_fn, consequent_fn, alternate_fn,
 		if_effect.f |= IS_ELSEIF;
 	}
 
-	mismatch = false; // TODO not sure if we actually need this — belt and braces
-
 	if_effect.ondestroy = () => {
 		// TODO make this unnecessary by linking the dom to the effect,
 		// and removing automatically on teardown