diff --git a/notebook/static/notebook/js/menubar.js b/notebook/static/notebook/js/menubar.js
index f795341e872..9d423736c34 100644
--- a/notebook/static/notebook/js/menubar.js
+++ b/notebook/static/notebook/js/menubar.js
@@ -136,8 +136,8 @@ define('notebook/js/menubar',[
         this.notebook.notebook_path
       );
 
-      const build_json_for_post = function(notebook, config, format) {
-        const json_to_pass = {
+      var build_json_for_post = function(notebook, config, format) {
+        var json_to_pass = {
           notebook_contents: {
             content: notebook.toJSON(),
             name: notebook.notebook_name,