Drone CI - missing `purge` when converting jsonnet to YAML

0-source-drone.jsonnet

local Pipeline(version) = {
  kind: "pipeline",
  steps: [
    {
      name: "build",
      image: "plugins/docker",
      settings: {
        dockerfile: "builder-" + version + ".dockerfile",
        registry: "img.company.com",
        repo: "img.company.com/builder",
        tags: version,
        purge: false
      }
    }
  ]
};

[
  Pipeline("1.0"),
  Pipeline("1.1")
]

1-output-drone.yml

---
kind: pipeline

platform:
  os: linux
  arch: amd64

steps:
- name: build
  image: plugins/docker
  settings:
    dockerfile: builder-1.0.dockerfile
    registry: img.company.com
    repo: img.company.com/builder
    tags: 1.0

---
kind: pipeline

platform:
  os: linux
  arch: amd64

steps:
- name: build
  image: plugins/docker
  settings:
    dockerfile: builder-1.1.dockerfile
    registry: img.company.com
    repo: img.company.com/builder
    tags: 1.1

...

99-details.log

$ drone --version
drone version 1.1.4

$ drone jsonnet --stream

$ echo $?
0