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: