--- charts-original/templates/statefulset.yaml
+++ charts/templates/statefulset.yaml
@@ -39,11 +39,13 @@
   - metadata:
       name: storage
     spec:
+{{- $_ := required "Must provide at least one access mode for persistent volumes used by Grafana" .Values.persistence.accessModes }}
+{{- $_ := required "Must provide at least one access mode for persistent volumes used by Grafana" (first .Values.persistence.accessModes) }}
       accessModes: {{ .Values.persistence.accessModes }}
       storageClassName: {{ .Values.persistence.storageClassName }}
       resources:
         requests:
-          storage: {{ .Values.persistence.size }}
+          storage: {{ required "Must provide size for persistent volumes used by Grafana" .Values.persistence.size }}
       {{- with .Values.persistence.selectorLabels }}
       selector:
         matchLabels: