diff --git a/monitoring/alert_rules.yml b/monitoring/alert_rules.yml
index 5a637d9..64faa13 100644
--- a/monitoring/alert_rules.yml
+++ b/monitoring/alert_rules.yml
@@ -151,7 +151,10 @@ groups:
           description: "Container CPU usage above 80% for 10 minutes."
 
       - alert: ContainerHighMemory
-        expr: container_memory_usage_bytes{name=~"performancewest-.*"} / container_spec_memory_limit_bytes{name=~"performancewest-.*"} * 100 > 85
+        expr: |
+          (container_memory_usage_bytes{name=~"performancewest-.*"}
+           / container_spec_memory_limit_bytes{name=~"performancewest-.*"} * 100 > 85)
+          and container_spec_memory_limit_bytes{name=~"performancewest-.*"} > 0
         for: 5m
         labels:
           severity: warning