--- a/misc/migration/3.18.0_Any.py	Thu Dec 12 14:25:24 2013 +0100
+++ b/misc/migration/3.18.0_Any.py	Thu Nov 14 17:17:02 2013 +0100
@@ -82,3 +82,10 @@
 schema.del_relation_def('CWAttribute', 'defaultval', 'String')
 
 commit()
+
+
+for rschema in schema.relations():
+    if rschema.symmetric:
+        with session.allow_all_hooks_but('activeintegrity'):
+            rql('SET X %(r)s Y WHERE Y %(r)s X, NOT X %(r)s Y' % {'r': rschema.type})
+    commit()