diff --git a/management/univention-management-console-module-diagnostic/umc/python/diagnostic/plugins/gateway.py b/management/univention-management-console-module-diagnostic/umc/python/diagnostic/plugins/gateway.py
index d7845e9..9784fe4 100644
--- a/management/univention-management-console-module-diagnostic/umc/python/diagnostic/plugins/gateway.py
+++ b/management/univention-management-console-module-diagnostic/umc/python/diagnostic/plugins/gateway.py
@@ -24,6 +24,8 @@
 def run():
 	ucr.load()
 	gateway = ucr.get('gateway')
+	if not gateway:
+		raise Critical(_('The gateway is not set.'))
 	process = Popen(['/bin/ping', '-c3', '-w4', '-W4', gateway], stdout=PIPE, stderr=STDOUT)
 	stdout, stderr = process.communicate()
 	if process.returncode: