diff --git a/templates/values.yaml.gotmpl b/templates/values.yaml.gotmpl
index 892f308..c9e8eec 100644
--- a/templates/values.yaml.gotmpl
+++ b/templates/values.yaml.gotmpl
@@ -146,7 +146,7 @@ prometheus:
     externalUrl: https://{{ .Values.cluster }}/prometheus/
     routePrefix: /prometheus/
     scrapeInterval: 10s
-    retention: 20d
+    retention: {{ if hasKey .Values "prometheusRetention" }}{{ .Values.prometheusRetention }}{{ else }}20d{{ end }}
     additionalScrapeConfigs:
 {{ readFile "scrape.yaml" | indent 6 }}
     storageSpec: