diff --git a/defaults/main.yml b/defaults/main.yml
index ac4177a..bb774e2 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -17,6 +17,9 @@ alertmanager_web_bind_ip: 127.0.0.1
 alertmanager_web_bind_port: 61001
 alertmanager_web_external_url: "http://localhost:61001/"
 
+alertmanager_cluster_bind_ip: 127.0.0.1
+alertmanager_cluster_bind_port: 61002
+
 alertmanager_web_tls_enabled: False
 alertmanager_web_tls_cert_path: "{{ alertmanager_base_dir }}/tls/certs/mycert.pem"
 alertmanager_web_tls_key_path: "{{ alertmanager_base_dir }}/tls/private/mykey.pem"
diff --git a/templates/etc/systemd/system/alertmanager.service.j2 b/templates/etc/systemd/system/alertmanager.service.j2
index 11959bb..9e81c8e 100644
--- a/templates/etc/systemd/system/alertmanager.service.j2
+++ b/templates/etc/systemd/system/alertmanager.service.j2
@@ -17,7 +17,7 @@ ExecStart={{ alertmanager_base_dir }}/alertmanager \
   --web.config.file={{ alertmanager_config_dir }}/web.yml \
   --web.listen-address={{ alertmanager_web_bind_ip }}:{{ alertmanager_web_bind_port }} \
   --web.external-url={{ alertmanager_web_external_url }} \
-  --cluster.listen-address= \
+  --cluster.listen-address={{ alertmanager_cluster_bind_ip }}:{{ alertmanager_cluster_bind_port }} \
 {% for flag in alertmanager_config_flags_extra %}
 {% if flag.value is not defined %}
   --{{ flag.name }} \