diff --git a/sourcing/static/js/doc.js b/sourcing/static/js/doc.js
index c0a90a2..d59d667 100644
--- a/sourcing/static/js/doc.js
+++ b/sourcing/static/js/doc.js
@@ -1,3 +1,5 @@
+'use strict';
+
 $(function() {
     $("div#right").hide();
     /* $("button#add-new-span").click(function() {