Slack notifications bug

I’m encountering the same issue, which I also mentioned here: Webhook notify depending on the branch

My webhook is hit for every branch I push (features, fixes, etc) even though I specify only wanting to notify on develop. Here’s the relevant part of circle.yml:

experimental:
  notify:
    branches:
      only:
        - develop

notify:
  webhooks:
    - url: https://domain.com/webhook