act: (bug) fromJSON leading to a yaml unmarshal error

This part of my GitHub Action workflow is confirmed to work on Github, but not through act:

strategy:
  matrix: ${{ fromJson(needs.deployments.outputs.deployments) }}

act -l

Error: yaml: unmarshal errors:
  line 153: cannot unmarshal !!str `${{ fro...` into map[string][]interface {}

The deployments output looks something like this:

[
  { "region": "us", "key": "value" },
  { "region": "eu", "key": "value2" }
]