diff --git a/resources/watch.js b/resources/watch.js
index cba3314274..b542fcf4b4 100644
--- a/resources/watch.js
+++ b/resources/watch.js
@@ -7,6 +7,8 @@
  * @noflow
  */
 
+'use strict';
+
 const sane = require('sane');
 const { resolve: resolvePath } = require('path');
 const { spawn } = require('child_process');