diff --git a/lib/main.html b/lib/main.html
index 4c10fcac..339767ba 100644
--- a/lib/main.html
+++ b/lib/main.html
@@ -67,6 +67,7 @@
   <script src="../node_modules/codemirror/mode/meta.js"></script>
   <script src="../node_modules/codemirror/addon/mode/overlay.js"></script>
   <script src="../node_modules/codemirror/addon/mode/loadmode.js"></script>
+  <script src="../node_modules/codemirror/addon/mode/simple.js"></script>
   <script src="../node_modules/codemirror/keymap/sublime.js"></script>
   <script src="../node_modules/codemirror/keymap/vim.js"></script>
   <script src="../node_modules/codemirror/keymap/emacs.js"></script>