diff -r 7518cb58ab4c -r 39df042f4ab4 cubicweb/server/sources/__init__.py
--- a/cubicweb/server/sources/__init__.py	Fri Sep 30 17:34:11 2016 +0200
+++ b/cubicweb/server/sources/__init__.py	Fri Sep 30 17:39:17 2016 +0200
@@ -342,8 +342,8 @@
 
     # system source interface #################################################
 
-    def eid_type_source(self, cnx, eid):
-        """return a tuple (type, extid, source) for the entity with id <eid>"""
+    def eid_type_extid(self, cnx, eid):
+        """return a tuple (type, extid) for the entity with id <eid>"""
         raise NotImplementedError(self)
 
     def create_eid(self, cnx):