--- a/management/univention-management-console-module-diagnostic/umc/python/diagnostic/plugins/46_kerberos_ddns_update.py	
+++ a/management/univention-management-console-module-diagnostic/umc/python/diagnostic/plugins/46_kerberos_ddns_update.py	
@@ -135,7 +135,7 @@ def check_nsupdate(config_registry):
 
 
 def run(_umc_instance):
-	if util.is_service_active('Samba 3'):
+	if not util.is_service_available('Samba 4'):
 		return  # ddns updates are not possible
 
 	config_registry = univention.config_registry.ConfigRegistry()
--- a/management/univention-management-console-module-diagnostic/umc/python/diagnostic/util.py	
+++ a/management/univention-management-console-module-diagnostic/umc/python/diagnostic/util.py	
@@ -45,3 +45,11 @@ def is_service_active(service):
 			return True
 	return False
 
+def is_service_available(service):
+	lo = univention.uldap.getMachineConnection()
+	raw_filter = '(univentionService=%s)'
+	filter_expr = ldap.filter.filter_format(raw_filter, (service,))
+	for (dn, _attr) in lo.search(filter_expr, attr=['cn']):
+		if dn is not None:
+			return True
+	return False