diff --git a/stateful/definition.py b/stateful/definition.py
index 4930e52..8e5cd0a 100644
--- a/stateful/definition.py
+++ b/stateful/definition.py
@@ -69,6 +69,8 @@ class Transition(Action):
 
     implements(ITransition)
 
+    actors = None
+
     def __init__(self, name, title, targetState, **kw):
         super(Transition, self).__init__(name, title, **kw)
         self.targetState = targetState