diff --git a/packages/svelte/tests/runtime-runes/samples/class-directive-mutations/main.svelte b/packages/svelte/tests/runtime-runes/samples/class-directive-mutations/main.svelte
index 6df1e1c39c..b3a77e4507 100644
--- a/packages/svelte/tests/runtime-runes/samples/class-directive-mutations/main.svelte
+++ b/packages/svelte/tests/runtime-runes/samples/class-directive-mutations/main.svelte
@@ -1,4 +1,6 @@
 <script>
+	import { onDestroy } from "svelte";
+
 	let {
         clazz = 'custom',
         foo = true,
@@ -32,6 +34,8 @@
         return result;
     }
 
+    onDestroy(() => { if (observer) observer.disconnect(); });
+
 </script>
 
 <main id="main" class:browser>