diff --git a/coap/coap.py b/coap/coap.py
index 74fef96..5b8c9b9 100644
--- a/coap/coap.py
+++ b/coap/coap.py
@@ -425,7 +425,7 @@ def _receive(self,timestamp,sender,rawbytes):
                     for (k,v) in self.transmitters.items():
                         # try matching
                         if (
-                                msgkey[0]==k[0] and
+                                u.ipv6AddrString2Bytes(msgkey[0])==u.ipv6AddrString2Bytes(k[0]) and
                                 msgkey[1]==k[1] and
                                 (
                                     msgkey[2]==k[2] or
diff --git a/coap/coapTransmitter.py b/coap/coapTransmitter.py
index 4b699c5..0d62811 100644
--- a/coap/coapTransmitter.py
+++ b/coap/coapTransmitter.py
@@ -200,7 +200,7 @@ def getState(self):
             return self.state
 
     def receiveMessage(self, timestamp, srcIp, srcPort, message):
-        assert srcIp==self.destIp
+        assert u.ipv6AddrString2Bytes(srcIp)==u.ipv6AddrString2Bytes(self.destIp)
         assert srcPort==self.destPort
         assert (message['token']==self.token) or (message['messageId']==self.messageId)