Cannot enable Pipelines - validator incorrectly fails on anchor reference

bitbucket-pipelines.yml files which utilize anchors for steps fail validation. For new projects this can cause Bitbucket to not allow Pipelines to be enabled.

example:

#!yaml

image: java:8
pipelines:
  default:
    - step: &buildSnapshot
        name: Build snapshot
        caches:
          - gradle
        script:
          - bash ./gradlew clean
          - bash ./gradlew build
  branches:
    develop:
      - step: *buildSnapshot
...

This script fails with 'missing required property 'script' on the final -step line.

Once the anchor reference was removed, I was able to enable Pipelines for the project. Re-adding the anchor reference once pipelines was enabled resulted in a successful build, with all steps executed as expected.