yaml intrinsic functions with omitted parameter convert to invalid null

[sparr]

test.yaml:

Fn::Include:
  location: test2.yaml

test2.yaml:

Name: !Select [ 0, !GetAZs ]

cfn-include test.yaml

{
  "Name": {
    "Fn::Select": [
      0,
      {
        "Fn::GetAZs": null
      }
    ]
  }
}

That most deeply nested line should be "Fn::GetAZs": "". CFN interprets a missing parameter in YAML as an empty string (afaict). The problem also occurs with YAML output.