diff --git a/dash/dash.py b/dash/dash.py
index 1b66150d66..fc7db45425 100644
--- a/dash/dash.py
+++ b/dash/dash.py
@@ -631,7 +631,7 @@ def dependencies(self):
                 'output': k,
                 'inputs': v['inputs'],
                 'state': v['state'],
-                'clientside_function': v.get('clientside_function', {})
+                'clientside_function': v.get('clientside_function', None)
             } for k, v in self.callback_map.items()
         ])