--- a/devtools/client/webconsole/test/test-bug-595934-workers.js
+++ b/devtools/client/webconsole/test/test-bug-595934-workers.js
@@ -1,9 +1,14 @@
 /* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
 /* vim: set ft=javascript ts=2 et sw=2 tw=80: */
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-onmessage = function () {
+/* global fooBarWorker*/
+/* eslint-disable no-unused-vars*/
+
+"use strict";
+
+var onmessage = function () {
   fooBarWorker();
 };