diff --git a/IPython/html/static/notebook/js/widgets/base.js b/IPython/html/static/notebook/js/widgets/base.js
index 1669e1a..d445e2b 100644
--- a/IPython/html/static/notebook/js/widgets/base.js
+++ b/IPython/html/static/notebook/js/widgets/base.js
@@ -557,4 +557,6 @@ function(widget_manager, underscore, backbone){
 
     IPython.WidgetModel = WidgetModel;
     IPython.WidgetView = WidgetView;
+
+    return widget_manager;
 });
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