diff --git a/notebook/static/notebook/js/notebook.js b/notebook/static/notebook/js/notebook.js
index 6f0694bf3..a04b99727 100644
--- a/notebook/static/notebook/js/notebook.js
+++ b/notebook/static/notebook/js/notebook.js
@@ -526,7 +526,8 @@ import {ShortcutEditor} from 'notebook/js/shortcuteditor';
      * @return {jQuery} A selector of all cell elements
      */
     Notebook.prototype.get_cell_elements = function () {
-        return this.container.find(".cell").not('.cell .cell');
+        var container = this.container || $('#notebook-container')
+        return container.find(".cell").not('.cell .cell');
     };
 
     /**
diff --git a/notebook/static/notebook/js/outputarea.js b/notebook/static/notebook/js/outputarea.js
index fd9f7d0a2..01a79c865 100644
--- a/notebook/static/notebook/js/outputarea.js
+++ b/notebook/static/notebook/js/outputarea.js
@@ -996,6 +996,15 @@ define([
         [MIME_JAVASCRIPT] : append_javascript,
         [MIME_PDF] : append_pdf
     };
+    
+    OutputArea.prototype.register_mime_type = function (mimetype, append, safe) {
+        if (mimetype && typeof(append) === 'function') {
+            OutputArea.output_types.push(mimetype);
+            if (safe) OutputArea.safe_outputs[mimetype] = true;
+            OutputArea.display_order.unshift(mimetype);
+            OutputArea.append_map[mimetype] = append;
+        }
+    };
 
     return {'OutputArea': OutputArea};
 });