Does anyone know how to properly configure ChartMuseum using s3 for backend storage?

I've followed the documentation and run

helm install --name my-chartmuseum -f custom.yaml stable/chartmuseum

With my custom.yaml as

env:
  open:
    DISABLE_API: false
    STORAGE: amazon
    STORAGE_AMAZON_BUCKET: chart-xxxx
    STORAGE_AMAZON_PREFIX: 
    STORAGE_AMAZON_REGION: eu-west-2

But the pod never enters a running state.

Has anyone actually done this?

I'm using Helm3 by the way.