OK, I've found it:
apt-get install tvheadend=4.1-1163~g1bf77c5~trusty
However, going to 1216 and back seems to have done something with my config which is not visible for me in the config pages. I can't tune anymore to anything back on 1163, all tuners show the state "bad" and in the log I receive RTSP errors -22 (Invalid Argument).
Rolling back the entire VM from the backup now ...