Notifications > Slack Channel name can only contain - as special characters

[mulantis]

Under System / Advanced / Notifications

I am attempting to change the Slack Channel name for notifications

eg: from "pfsense"
to "pfsense_alerts"

I make the change, and sucessfully send a "Test Slack Settings"
but when clicking Save:

The following input errors were detected:
The Slack Channel name can only contain - as special characters

I suspect this could be a UI bug.

[wouterros]

@mulantis Same error here, even if i create a new channel in slack and try to save. Did you manage to find something?
Thanks