diff --git a/charts/flagger/templates/prometheus.yaml b/charts/flagger/templates/prometheus.yaml
index b15f50e1..24e0fc02 100644
--- a/charts/flagger/templates/prometheus.yaml
+++ b/charts/flagger/templates/prometheus.yaml
@@ -233,7 +233,7 @@ spec:
           image: {{ .Values.prometheus.image }}
           imagePullPolicy: IfNotPresent
           args:
-            - '--storage.tsdb.retention={{ .Values.prometheus.retention }}'
+            - '--storage.tsdb.retention.time={{ .Values.prometheus.retention }}'
             - '--config.file=/etc/prometheus/prometheus.yml'
           ports:
             - containerPort: 9090