diff --git a/__init__.py b/__init__.py
index b853f6e..ce20ae1 100644
--- a/__init__.py
+++ b/__init__.py
@@ -83,7 +83,7 @@ class mqtt_client(object):
 
     def __receive__(self, client, userdata, message):
         logger.debug("Received message with topic %s and payload %s", message.topic, str(message.payload))
-        for topic in self.__callbacks__:
+        for topic in self.__callbacks__.copy():
             if topic.endswith('#'):
                 if message.topic.startswith(topic[:-1]):
                     self.__callbacks__[topic](client, userdata, message)