diff --git a/IPython/html/static/notebook/js/notificationarea.js b/IPython/html/static/notebook/js/notificationarea.js
index d496584ba..6566667ae 100644
--- a/IPython/html/static/notebook/js/notificationarea.js
+++ b/IPython/html/static/notebook/js/notificationarea.js
@@ -91,7 +91,7 @@ define([
         });
 
         // Implicitly start off in Command mode, switching to Edit mode will trigger event
-        $modal_ind_icon.attr('class','command-mode_icon').attr('title','Command Mode');
+        $modal_ind_icon.attr('class','command_mode_icon').attr('title','Command Mode');
 
         // Kernel events
         this.events.on('status_idle.Kernel',function () {