Alert in alertmanager UI it's trying to redirecting to http://prometheus:8080

Hello team,
Configured prometheus server and kept behind nginx (URL :
Configured Alertmanager server and kept behind nginx (URL :

When i click on received Email alert i am redirecting to right prometheus instance.
But when i click on alert in alertmanager UI it’s trying to redirecting to http://prometheus:8080, any help i can get where to configure the URL ?