diff --git a/services/univention-s4-connector/modules/univention/s4connector/s4/__init__.py b/services/univention-s4-connector/modules/univention/s4connector/s4/__init__.py
index fe16a00465..56ab7330ad 100644
--- a/services/univention-s4-connector/modules/univention/s4connector/s4/__init__.py
+++ b/services/univention-s4-connector/modules/univention/s4connector/s4/__init__.py
@@ -1333,7 +1333,7 @@ class s4(univention.s4connector.ucs):
 		ud.debug(ud.LDAP, ud.INFO, "group_members_sync_from_ucs: UCS-members in s4_members_from_ucs %s" % s4_members_from_ucs)
 
 		# check if members in S4 don't exist in UCS, if true they need to be added in S4
-		for member_dn in s4_members_from_ucs:
+		for member_dn in s4_members:
 			if not member_dn.lower() in s4_members_from_ucs:
 				try:
 					ad_object = self.get_object(member_dn)