diff --git a/demo/index.html b/demo/index.html
index d4574aa3b..ce58e1923 100644
--- a/demo/index.html
+++ b/demo/index.html
@@ -5,6 +5,7 @@
         <link rel="stylesheet" href="/build/xterm.css" />
         <link rel="stylesheet" href="/build/addons/fullscreen/fullscreen.css" />
         <link rel="stylesheet" href="style.css" />
+      	<script src="https://cdnjs.cloudflare.com/ajax/libs/es6-promise/4.1.1/es6-promise.auto.min.js"></script>
       	<script src="https://cdnjs.cloudflare.com/ajax/libs/fetch/1.0.0/fetch.min.js"></script>
         <script src="/build/xterm.js" ></script>
         <script src="/build/addons/attach/attach.js" ></script>