diff --git a/IPython/html/static/notebook/js/toolbar.js b/IPython/html/static/notebook/js/toolbar.js
index 3b313eeb4..924368caa 100644
--- a/IPython/html/static/notebook/js/toolbar.js
+++ b/IPython/html/static/notebook/js/toolbar.js
@@ -79,8 +79,7 @@ define([
     };
 
     ToolBar.prototype.style = function () {
-        this.element.addClass('border-box-sizing')
-            .addClass('toolbar');
+        this.element.addClass('toolbar');
     };
 
     /**
diff --git a/IPython/html/static/notebook/less/toolbar.less b/IPython/html/static/notebook/less/toolbar.less
index 7b160b28c..26f7cf67e 100644
--- a/IPython/html/static/notebook/less/toolbar.less
+++ b/IPython/html/static/notebook/less/toolbar.less
@@ -18,6 +18,8 @@
     .btn {
         padding: 2px 8px;
     }
+
+    .border-box-sizing();
 }
 
 .toolbar .btn-group {
@@ -40,7 +42,7 @@
     text-align: right;
     margin-left: 5px;
     margin-right: 0px;
-    margin-top: 0px
+    margin-top: 0px;
   }
 
   .toolbar {