add missing ingressClassName
diff --git a/docs/monitoring.md b/docs/monitoring.md
index dc924f3..9f702f1 100644
--- a/docs/monitoring.md
+++ b/docs/monitoring.md
@@ -44,6 +44,7 @@
   alertmanager:
     ingress:
       enabled: true
+      ingressClassName: openstack
       annotations:
         cert-manager.io/cluster-issuer: atmosphere
       hosts:
@@ -80,6 +81,7 @@
   alertmanager:
     ingress:
       enabled: true
+      ingressClassName: openstack
       annotations:
         cert-manager.io/cluster-issuer: atmosphere
         nginx.ingress.kubernetes.io/auth-type: basic