[SOLVED] dm-crypt "Cannot use serpent-xts-plain64 cipher for keyslot encryption." After migration to LUKS2

Hi,

I'm trying to migrate to luks2 header format, and on first try I got hit with Quote:

Cannot use serpent-xts-plain64 cipher for keyslot encryption.

after running Code:cryptsetup convertrestoring the header worked fine, so no data loss. Any ideas?
cryptsetup version 2.3.4

The only reference I found on the net is here (askubuntu.com). But without answer...

Thanks.