diff --git a/test/runtime/samples/keyed-each-dev-unique/_config.js b/test/runtime/samples/keyed-each-dev-unique/_config.js
new file mode 100644
index 0000000000..8f46af9d52
--- /dev/null
+++ b/test/runtime/samples/keyed-each-dev-unique/_config.js
@@ -0,0 +1,7 @@
+export default {
+	compileOptions: {
+		dev: true
+	},
+
+	error: `Cannot have duplicate keys in a keyed each`
+};
diff --git a/test/runtime/samples/keyed-each-dev-unique/main.svelte b/test/runtime/samples/keyed-each-dev-unique/main.svelte
new file mode 100644
index 0000000000..870e7beaa1
--- /dev/null
+++ b/test/runtime/samples/keyed-each-dev-unique/main.svelte
@@ -0,0 +1,7 @@
+<script>
+	const array = [1, 2, 3, 1];
+</script>
+
+{#each array as item (item)}
+	{item}
+{/each}