diff --git a/management/univention-management-console/src/univention/management/console/protocol/server.py b/management/univention-management-console/src/univention/management/console/protocol/server.py
index 9f4adf4..13edf47 100644
--- a/management/univention-management-console/src/univention/management/console/protocol/server.py
+++ b/management/univention-management-console/src/univention/management/console/protocol/server.py
@@ -139,7 +139,10 @@ def _receive(self, socket):
 			self._cleanup(socket)
 			return False
 
-		state = self.__states[socket]
+		try:
+			state = self.__states[socket]
+		except KeyError:
+			return False
 		state.buffer += data
 
 		msg = None
@@ -209,7 +212,10 @@ def _handle(self, state, msg):
 			state.processor.request(msg)
 
 	def _do_send(self, socket):
-		state = self.__states[socket]
+		try:
+			state = self.__states[socket]
+		except KeyError:
+			return False
 		id, first = state.resend_queue.pop(0)
 		try:
 			ret = socket.send(first)