[knot-dns-users] Old key is being used

Hi, we performed successfully an algorithm rollover. After changing the algorithm in the configuration file everything worked as expected. All zones have been updated to the new algorithm. When I now sign a new zone the zone is being signed with the old algorithm's key and an algorithm rollover is being triggered immediately. Is this an expected behavior? How can I avoid this? Do I have to delete the old key? Thanks a lot, Thomas