diff --git a/platform/firefox/frameScript.js b/platform/firefox/frameScript.js
index d1ae54a28..c93c7e006 100644
--- a/platform/firefox/frameScript.js
+++ b/platform/firefox/frameScript.js
@@ -21,8 +21,6 @@
 
 /* globals Services, sendAsyncMessage, addMessageListener, removeMessageListener */
 
-'use strict';
-
 /******************************************************************************/
 
 (function(frameScriptContext) {