diff --git a/test/runtime/samples/reactive-values-subscript-assignment/_config.js b/test/runtime/samples/reactive-values-subscript-assignment/_config.js
new file mode 100644
index 0000000000..e29fe2c676
--- /dev/null
+++ b/test/runtime/samples/reactive-values-subscript-assignment/_config.js
@@ -0,0 +1,11 @@
+export default {
+	test({ assert, component }) {
+		assert.deepEqual(component.foo, {});
+		component.bar = 'hello';
+		assert.deepEqual(component.foo, { hello: true });
+		component.bar = 'world';
+		assert.deepEqual(component.foo, { hello: true, world: true });
+		component.bar = false;
+		assert.deepEqual(component.foo, { hello: true, world: true });
+	}
+};
diff --git a/test/runtime/samples/reactive-values-subscript-assignment/main.svelte b/test/runtime/samples/reactive-values-subscript-assignment/main.svelte
new file mode 100644
index 0000000000..9753032618
--- /dev/null
+++ b/test/runtime/samples/reactive-values-subscript-assignment/main.svelte
@@ -0,0 +1,7 @@
+<script>
+	export let foo = {};
+	export let bar;
+	$: if (bar) {
+		foo[bar] = true;
+	}
+</script>