How can I connect a private Slack channel to a BitBucket Cloud repository?

[eproxus]

When trying to add a subscription to a private BitBucket Cloud repository for a private Slack channel with some single-channel guest accounts invited, I get this message:

Sorry, but I can't post notifications inside a direct message with someone else yet, but you can get notifications in a direct message with me. I'll send you a message and we can get started.

According to the documentation this should be possible. How can I add repository notifications for private channels?

[eproxus · Accepted solution]

By going to Settings → Chat Notifications → Settings and adding the Slack integration from there to the private channel, it works.