diff --git a/management/univention-directory-manager-modules/modules/univention/admin/handlers/users/user.py b/management/univention-directory-manager-modules/modules/univention/admin/handlers/users/user.py
index f438f52430..d5a9052325 100644
--- a/management/univention-directory-manager-modules/modules/univention/admin/handlers/users/user.py
+++ b/management/univention-directory-manager-modules/modules/univention/admin/handlers/users/user.py
@@ -2270,7 +2270,7 @@ class object(univention.admin.handlers.simpleLdap):
 
 	def _modlist_univention_person(self, ml):
 		# make sure that univentionPerson is set as objectClass when needed
-		if any(self.hasChanged(ikey) and self[ikey] for ikey in ('umcProperty', 'birthday')):
+		if any(self.hasChanged(ikey) and self[ikey] for ikey in ('umcProperty', 'birthday')) and 'univentionPerson' not in self.oldattr.get('objectClass', []):
 			ml.append(('objectClass', '', 'univentionPerson'))  # TODO: check if exists already
 		return ml