diff --git a/dom/events/AddEventListenerOptions-signal.any.js b/dom/events/AddEventListenerOptions-signal.any.js
index 9f5539ee7a40a0..ecb475713461af 100644
--- a/dom/events/AddEventListenerOptions-signal.any.js
+++ b/dom/events/AddEventListenerOptions-signal.any.js
@@ -1,3 +1,5 @@
+'use strict';
+
 test(function() {
   let count = 0;
   function handler() {