Slack Integration - Only want status for the Master branch of my projects

I have setup the slack/circle CI integration. It works and I have reduced the noise by selecting Fixed/Failed Only. But what I really want to to only get notified on failures/fixed for the master branch. Is there a way to do without using the experimental flag for each individual repo (I am working with over 50 repos and that would be too much work).



There is now an option for this: