[Koha] Upgrading from 19.11.29.000 to latest

I've upgraded my OS from Jessie to Stretch, and am now trying to upgrade a Koha Debian package install from 19.11.29.000 to the latest, but the schema upgrade fails with this: * Upgrade to 22.06.00.077 [23:48:59]: ERROR: {UNKNOWN}: Can't use an undefined value as a subroutine reference at /usr/share/koha/lib/C4/Installer.pm line 737. at /usr/share/koha/lib/C4/Installer.pm line 739 I've searched Bugzilla and don't' seem to find anything similar. Anyone have any idea what might cause this? Missing some package perhaps? Cheers! Steve