Ardour 3 beta5 Punch in recording active - no playback

With punch-in and global recording activated I get no playback from the armed channel while playhead is running towards the punch-in position, no matter if in tape or normal mode. The indicators of the channel strip show ‘Disk’ before and change to ‘In’ after crossing the punch position but there is no sound anyway. I could not find a way to get this working, Perhaps I’m too stupid, but in Ardour 2 it worked perfectly. Any solution??