diff --git a/sleekxmpp/clientxmpp.py b/sleekxmpp/clientxmpp.py
index 34d8008..0d5c85b 100644
--- a/sleekxmpp/clientxmpp.py
+++ b/sleekxmpp/clientxmpp.py
@@ -234,7 +234,7 @@ class ClientXMPP(BaseXMPP):
                                        'subscription': subscription,
                                        'groups': groups}}
         response = iq.send(block, timeout, callback)
-        if response in [False, None]:
+        if response in [False, None] or not isinstance(response, Iq):
             return response
         return response['type'] == 'result'