diff --git a/src/message_control.py b/src/message_control.py
index addb17111..4c58c5a92 100644
--- a/src/message_control.py
+++ b/src/message_control.py
@@ -219,6 +219,7 @@ class MessageControl(object):
     def remove_session(self, session):
         if session != self.session:
             return
+        self.session.control = None
         self.session = None
 
     def _nec_message_outgoing(self, obj):