Skaffold deploy not passing flags to Helm

[bhardwick]

I have tried the following variations to send the --history-max 1 flag to Helm:

deploy:
  helm:
    releases:
      - name: my-app
    flags:
      upgrade: ["--history-max", "1"]

deploy:
  helm:
    releases:
      - name: my-app
    flags:
      upgrade: ["--history-max=1"]

deploy:
  helm:
    releases:
      - name: my-app
    flags:
      upgrade:
        - "--history-max=1"

However, Skaffold ignores this option: Running command: [helm --kube-context gke_gcp-my-cluster-dev upgrade my-app skaffold/helm --post-renderer /usr/bin/skaffold --namespace test -f skaffold/helm/values/globals.yml -f skaffold/helm/values/values-dev.yml]

What is the correct way to pass flags to Helm upgrade?