diff --git a/notebook/notebookapp.py b/notebook/notebookapp.py
index d9a1fd4fe..b9d04eefa 100755
--- a/notebook/notebookapp.py
+++ b/notebook/notebookapp.py
@@ -232,7 +232,7 @@ class NotebookWebApplication(web.Application):
             },
             version_hash=version_hash,
             ignore_minified_js=jupyter_app.ignore_minified_js,
-            
+
             # rate limits
             iopub_msg_rate_limit=jupyter_app.iopub_msg_rate_limit,
             iopub_data_rate_limit=jupyter_app.iopub_data_rate_limit,
@@ -242,7 +242,7 @@ class NotebookWebApplication(web.Application):
             # tornado defaults are 100 MiB, we increase it to 0.5 GiB
             max_body_size = 512 * 1024 * 1024,
             max_buffer_size = 512 * 1024 * 1024,
-            
+
             # authentication
             cookie_secret=jupyter_app.cookie_secret,
             login_url=url_path_join(base_url,'/login'),
@@ -264,6 +264,8 @@ class NotebookWebApplication(web.Application):
 
             # Jupyter stuff
             started=now,
+            # place for extensions to register activity
+            activity_sources={},
             jinja_template_vars=jupyter_app.jinja_template_vars,
             nbextensions_path=jupyter_app.nbextensions_path,
             websocket_url=jupyter_app.websocket_url,
@@ -360,6 +362,7 @@ class NotebookWebApplication(web.Application):
             sources.append(self.settings['terminal_last_activity'])
         except KeyError:
             pass
+        sources.extend(self.settings['activity_sources'].values())
         return max(sources)