diff --git a/management/univention-directory-manager-modules/modules/univention/admin/handlers/computers/domaincontroller_backup.py b/management/univention-directory-manager-modules/modules/univention/admin/handlers/computers/domaincontroller_backup.py
index ef7b571..b97246c 100644
--- a/management/univention-directory-manager-modules/modules/univention/admin/handlers/computers/domaincontroller_backup.py
+++ b/management/univention-directory-manager-modules/modules/univention/admin/handlers/computers/domaincontroller_backup.py
@@ -517,9 +517,10 @@ def _ldap_addlist(self):
 			self.alloc.append(('uidNumber',self.uidNum))
 			gidNum='99999'
 			if self['primaryGroup']:
-				searchResult = self.lo.getAttr(self['primaryGroup'], 'gidNumber')
-				if searchResult:
-					gidNum = searchResult[0]
+				try:
+					gidNum = self.lo.getAttr(self['primaryGroup'], 'gidNumber', required=True)[0]
+				except ldap.NO_SUCH_OBJECT:
+					raise univention.admin.uexceptions.primaryGroup(self['primaryGroup'])
 			ocs.extend(['posixAccount','shadowAccount'])
 			al.append(('uidNumber', [self.uidNum]))
 			al.append(('gidNumber', [gidNum]))