diff --git a/packages/svelte/tests/runtime-runes/samples/untrack-allows-writes/_config.js b/packages/svelte/tests/runtime-runes/samples/untrack-allows-writes/_config.js
new file mode 100644
index 0000000000..ead5653dd4
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/untrack-allows-writes/_config.js
@@ -0,0 +1,19 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+// While we don't officially document it, `untrack` also allows to opt out of the "unsafe mutation" validation, which is what we test here
+export default test({
+	html: '<button>0 0 0</button>',
+	test({ assert, target }) {
+		const button = target.querySelector('button');
+
+		flushSync(() => button?.click());
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>1 1 2</button>
+			`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/untrack-allows-writes/main.svelte b/packages/svelte/tests/runtime-runes/samples/untrack-allows-writes/main.svelte
new file mode 100644
index 0000000000..f61a23da84
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/untrack-allows-writes/main.svelte
@@ -0,0 +1,14 @@
+<script>
+	import { untrack } from "svelte";
+
+	let count = $state(0);
+	let mirrored = $state(0);
+	let double = $derived.by(() => {
+		untrack(() => {
+			mirrored = count;
+		});
+		return count * 2;
+	})
+</script>
+
+<button onclick={() => count++}>{count} {mirrored} {double}</button>