Deployments API - trigger workflow based on Deployment to specific environment or branch

Hi folks,

We’re hoping to leverage the Deployments API as a natural way to handle our deployments. Unfortunately, we are not having any luck triggering a workflow based on a Deployment to a specific branch or environment, e.g.:

on:
  deployment:
    branches:
      - master

or

on:
  deployment:
    environments:
      - dev

do not seem to work. Instead, they seem to trigger a workflow for each environment we have defined in the repo. Is triggering a workflow based on the Deployments API presently only supported if you have all of your environments based on a single workflow with conditional logic to determine what should run? Or are we missing something?