--- a/devtools/testlib.py	Tue Dec 08 13:59:47 2009 +0100
+++ b/devtools/testlib.py	Tue Dec 08 14:42:03 2009 +0100
@@ -756,7 +756,7 @@
             rset = cu.execute('%s X' % etype)
             edict[str(etype)] = set(row[0] for row in rset.rows)
         existingrels = {}
-        ignored_relations = SYSTEM_RELATIONS + self.ignored_relations
+        ignored_relations = SYSTEM_RELATIONS | self.ignored_relations
         for rschema in self.schema.relations():
             if rschema.final or rschema in ignored_relations:
                 continue