diff --git a/core/misc/announce.js b/core/misc/announce.js
index ed0203857a2da0e63172497d25d6d2a13f042445..3037436b008b5eb217f880a5a3be7735b4dd943c 100644
--- a/core/misc/announce.js
+++ b/core/misc/announce.js
@@ -16,6 +16,8 @@
  */
 (function (Drupal, debounce) {
 
+  "use strict";
+
   var liveElement;
   var announcements = [];