diff --git a/IPython/html/static/notebook/js/main.js b/IPython/html/static/notebook/js/main.js
index 62bac93..4ddee4b 100644
--- a/IPython/html/static/notebook/js/main.js
+++ b/IPython/html/static/notebook/js/main.js
@@ -42,8 +42,6 @@ require([
     ) {
     "use strict";
 
-    $('div#notebook_panel').addClass('border-box-sizing');
-
     var common_options = {
         base_url : utils.get_body_data("baseUrl"),
         ws_url : IPython.utils.get_body_data("wsUrl"),
diff --git a/IPython/html/static/notebook/less/notebook.less b/IPython/html/static/notebook/less/notebook.less
index 1c93a7b..1592fa3 100644
--- a/IPython/html/static/notebook/less/notebook.less
+++ b/IPython/html/static/notebook/less/notebook.less
@@ -31,6 +31,7 @@ div#notebook_panel {
     margin: 0px 0px 0px 0px;
     padding: 0px;
     .box-shadow(@notebook-shadow);
+    .border-box-sizing();
 }
 div#notebook {
     font-size: @notebook_font_size;