--- a/src/core/xmpp.py	Tue Dec 12 01:07:25 2017 +0100
+++ b/src/core/xmpp.py	Wed Jan 03 00:13:48 2018 +0100
@@ -356,6 +356,9 @@
             subject = {}
         if extra is None:
             extra = {}
+
+        assert mess_type in C.MESS_TYPE_ALL
+
         data = {  # dict is similar to the one used in client.onMessage
             "from": self.jid,
             "to": to_jid,
@@ -369,10 +372,10 @@
         pre_xml_treatments = defer.Deferred() # XXX: plugin can add their pre XML treatments to this deferred
         post_xml_treatments = defer.Deferred() # XXX: plugin can add their post XML treatments to this deferred
 
-        if data["type"] == "auto":
+        if data["type"] == C.MESS_TYPE_AUTO:
             # we try to guess the type
             if data["subject"]:
-                data["type"] = 'normal'
+                data["type"] = C.MESS_TYPE_NORMAL
             elif not data["to"].resource:  # if to JID has a resource, the type is not 'groupchat'
                 # we may have a groupchat message, we check if the we know this jid
                 try:
@@ -382,12 +385,12 @@
                     entity_type = "contact"
 
                 if entity_type == "chatroom":
-                    data["type"] = 'groupchat'
+                    data["type"] = C.MESS_TYPE_GROUPCHAT
                 else:
-                    data["type"] = 'chat'
+                    data["type"] = C.MESS_TYPE_CHAT
             else:
-                data["type"] == 'chat'
-            data["type"] == "chat" if data["subject"] else "normal"
+                data["type"] == C.MESS_TYPE_CHAT
+            data["type"] == C.MESS_TYPE_CHAT if data["subject"] else C.MESS_TYPE_NORMAL
 
         # FIXME: send_only is used by libervia's OTR plugin to avoid
         #        the triggers from frontend, and no_trigger do the same