diff --git a/jsonnet/kube-prometheus/alerts/alertmanager.libsonnet b/jsonnet/kube-prometheus/alerts/alertmanager.libsonnet
index 42ae3f98353e23d5d4dbc527ff3d17b7a4018220..bf58862dd26a16b718a2b3d931faa0ef2819d744 100644
--- a/jsonnet/kube-prometheus/alerts/alertmanager.libsonnet
+++ b/jsonnet/kube-prometheus/alerts/alertmanager.libsonnet
@@ -37,7 +37,7 @@
             },
             expr: |||
               alertmanager_cluster_members{%(alertmanagerSelector)s}
-                != on (service)
+                != on (service) GROUP_LEFT()
               count by (service) (alertmanager_cluster_members{%(alertmanagerSelector)s})
             ||| % $._config,
             'for': '5m',
diff --git a/jsonnet/kube-prometheus/alerts/tests.yaml b/jsonnet/kube-prometheus/alerts/tests.yaml
index 8cfc3aa7c648c6a273803a7f7ef52f4e1079d8a2..532bb895561757e0024a66ef045dbce11f90afc8 100644
--- a/jsonnet/kube-prometheus/alerts/tests.yaml
+++ b/jsonnet/kube-prometheus/alerts/tests.yaml
@@ -24,6 +24,10 @@ tests:
           - exp_labels:
               service: 'alertmanager-main'
               severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.0
+              namespace: monitoring
+              pod: alertmanager-main-0
             exp_annotations:
               message: 'Alertmanager has not found all other members of the cluster.'
       - eval_time: 17m
@@ -32,6 +36,10 @@ tests:
           - exp_labels:
               service: 'alertmanager-main'
               severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.0
+              namespace: monitoring
+              pod: alertmanager-main-0
             exp_annotations:
               message: 'Alertmanager has not found all other members of the cluster.'
       - eval_time: 23m
@@ -40,5 +48,110 @@ tests:
           - exp_labels:
               service: 'alertmanager-main'
               severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.0
+              namespace: monitoring
+              pod: alertmanager-main-0
+            exp_annotations:
+              message: 'Alertmanager has not found all other members of the cluster.'
+  - interval: 1m
+    input_series:
+      - series: 'alertmanager_cluster_members{job="alertmanager-main",instance="10.10.10.0",namespace="monitoring",pod="alertmanager-main-0",service="alertmanager-main"}'
+        values: '3 3 3 3 3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1'
+      - series: 'alertmanager_cluster_members{job="alertmanager-main",instance="10.10.10.1",namespace="monitoring",pod="alertmanager-main-1",service="alertmanager-main"}'
+        values: '3 3 3 3 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2'
+      - series: 'alertmanager_cluster_members{job="alertmanager-main",instance="10.10.10.2",namespace="monitoring",pod="alertmanager-main-2",service="alertmanager-main"}'
+        values: '3 3 3 3 3 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2'
+    alert_rule_test:
+      - eval_time: 5m
+        alertname: AlertmanagerMembersInconsistent
+      - eval_time: 11m
+        alertname: AlertmanagerMembersInconsistent
+        exp_alerts:
+          - exp_labels:
+              service: 'alertmanager-main'
+              severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.0
+              namespace: monitoring
+              pod: alertmanager-main-0
+            exp_annotations:
+              message: 'Alertmanager has not found all other members of the cluster.'
+          - exp_labels:
+              service: 'alertmanager-main'
+              severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.1
+              namespace: monitoring
+              pod: alertmanager-main-1
+            exp_annotations:
+              message: 'Alertmanager has not found all other members of the cluster.'
+          - exp_labels:
+              service: 'alertmanager-main'
+              severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.2
+              namespace: monitoring
+              pod: alertmanager-main-2
+            exp_annotations:
+              message: 'Alertmanager has not found all other members of the cluster.'
+      - eval_time: 17m
+        alertname: AlertmanagerMembersInconsistent
+        exp_alerts:
+          - exp_labels:
+              service: 'alertmanager-main'
+              severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.0
+              namespace: monitoring
+              pod: alertmanager-main-0
+            exp_annotations:
+              message: 'Alertmanager has not found all other members of the cluster.'
+          - exp_labels:
+              service: 'alertmanager-main'
+              severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.1
+              namespace: monitoring
+              pod: alertmanager-main-1
+            exp_annotations:
+              message: 'Alertmanager has not found all other members of the cluster.'
+          - exp_labels:
+              service: 'alertmanager-main'
+              severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.2
+              namespace: monitoring
+              pod: alertmanager-main-2
+            exp_annotations:
+              message: 'Alertmanager has not found all other members of the cluster.'
+      - eval_time: 23m
+        alertname: AlertmanagerMembersInconsistent
+        exp_alerts:
+          - exp_labels:
+              service: 'alertmanager-main'
+              severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.0
+              namespace: monitoring
+              pod: alertmanager-main-0
+            exp_annotations:
+              message: 'Alertmanager has not found all other members of the cluster.'
+          - exp_labels:
+              service: 'alertmanager-main'
+              severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.1
+              namespace: monitoring
+              pod: alertmanager-main-1
+            exp_annotations:
+              message: 'Alertmanager has not found all other members of the cluster.'
+          - exp_labels:
+              service: 'alertmanager-main'
+              severity: critical
+              job: 'alertmanager-main'
+              instance: 10.10.10.2
+              namespace: monitoring
+              pod: alertmanager-main-2
             exp_annotations:
               message: 'Alertmanager has not found all other members of the cluster.'
diff --git a/jsonnetfile.lock.json b/jsonnetfile.lock.json
index 3b9d80cd6aac08ebbdb928e549260864cb1b09a0..3665f14f323d6070ed73e18a3ede39c959be4f3a 100644
--- a/jsonnetfile.lock.json
+++ b/jsonnetfile.lock.json
@@ -8,7 +8,7 @@
                     "subdir": "contrib/kube-prometheus/jsonnet/kube-prometheus"
                 }
             },
-            "version": "dff8f44fbce268596c86b8d586c64c17953feab3"
+            "version": "9cc151ced4308573a91f4cc3fcdbc951213b03e0"
         },
         {
             "name": "ksonnet",
diff --git a/manifests/prometheus-rules.yaml b/manifests/prometheus-rules.yaml
index a7987abc6c1b5ebc5ce9e0c96766931a86be774f..872cf310546dc184770c9203b0c90585816dd065 100644
--- a/manifests/prometheus-rules.yaml
+++ b/manifests/prometheus-rules.yaml
@@ -790,7 +790,7 @@ spec:
         message: Alertmanager has not found all other members of the cluster.
       expr: |
         alertmanager_cluster_members{job="alertmanager-main"}
-          != on (service)
+          != on (service) GROUP_LEFT()
         count by (service) (alertmanager_cluster_members{job="alertmanager-main"})
       for: 5m
       labels: