diff --git a/horizon/server/cluster.yml b/horizon/server/cluster.yml
index 06a720c..837d9b5 100644
--- a/horizon/server/cluster.yml
+++ b/horizon/server/cluster.yml
@@ -1,6 +1,7 @@
 classes:
 - service.keepalived.cluster.single
 - service.horizon.server.cluster
+- system.horizon.upgrade
 - system.horizon.server.iptables
 - service.haproxy.proxy.single
 - system.apache.server.single