I'm trying to get caching working on my Kubernetes powered Gitlab Runner. I've set up a custom S3 Minio Deployment running on minio:9000 and configured the config.toml file using a ConfigMap with this content:

concurrent = 10 # This sets the maximum number of concurrent CI pods
check_interval = 10

[[runners]]
  [runners.cache]
    Type = "s3"
    Path = "cache"
    Shared = true
    [runners.cache.s3]
      ServerAddress = "minio:9000"
      AccessKey = "xxx"
      SecretKey = "xxx"
      BucketName = "runners-cache"
      Insecure = true

Using the Minio web interface, I've made sure there is a runners-cache bucket present.

However, inside the job I get:

Checking cache for default...
No URL provided, cache will not be downloaded from shared cache server. Instead a local version of cache will be extracted. 

And inside the logs on the runner, I get:

 Could not create cache adapter
 cache factory not found: factory for cache adapter "" was not registered

What am I missing?