diff --git a/management/univention-directory-manager-modules/modules/univention/admin/handlers/__init__.py b/management/univention-directory-manager-modules/modules/univention/admin/handlers/__init__.py
index b88af05..866be35 100644
--- a/management/univention-directory-manager-modules/modules/univention/admin/handlers/__init__.py
+++ b/management/univention-directory-manager-modules/modules/univention/admin/handlers/__init__.py
@@ -2430,14 +2430,16 @@ def update_groups(self):
 				return
 		univention.debug.debug(univention.debug.ADMIN, univention.debug.INFO, 'updating groups')
 
+		def _append_dn(from_, target, dn):
+			if not any(self.lo.lo.compare_dn(x, dn) for x in from_):
+				target.append(dn)
+
 		add_to_group = []
 		remove_from_group = []
 		for group in self.oldinfo.get('groups', []):
-			if group not in self.info.get('groups', []):
-				remove_from_group.append(group)
+			_append_dn(self.info.get('groups', []), remove_from_group, group)
 		for group in self.info.get('groups', []):
-			if group not in self.oldinfo.get('groups', []):
-				add_to_group.append(group)
+			_append_dn(self.oldinfo.get('groups', []), add_to_group, group)
 
 		if 'oldPrimaryGroupDn' in self.__dict__:
 			if self.oldPrimaryGroupDn:
@@ -2455,14 +2457,14 @@ def update_groups(self):
 		for group in add_to_group:
 			groupObject = univention.admin.objects.get(univention.admin.modules.get('groups/group'), self.co, self.lo, self.position, group)
 			groupObject.open()
-			if self.dn not in groupObject['hosts']:
+			if not any(self.lo.lo.compare_dn(x, self.dn) for x in groupObject['hosts']):
 				groupObject['hosts'].append(self.dn)
 				groupObject.modify(ignore_license=1)
 
 		for group in remove_from_group:
 			groupObject = univention.admin.objects.get(univention.admin.modules.get('groups/group'), self.co, self.lo, self.position, group)
 			groupObject.open()
-			if self.dn in groupObject['hosts']:
+			if not any(self.lo.lo.compare_dn(x, self.dn) for x in groupObject['hosts']):
 				groupObject['hosts'].remove(self.dn)
 				groupObject.modify(ignore_license=1)