unsupport release version error in jail ports after upgrading to 12.1-p2

[David Mehler]

Hello,

I've upgraded a system from FreeBSD 12.0-p13 to FreeBSD 12.1-P2 on the
host system everything went fine. I've got three jails running on it.
After I did completed the host upgrade I upgraded each of the jails
with this:

freebsd-update -f /etc/jail-freebsd-update.conf -b
/usr/jails/jail_name/ --currently-running `jexec -l Jail_name
freebsd-version` fetch install

I've got the host's ports tree nullfs mounted in each jail and the
upgrade process appeared to work properly. On the host and in each
jail uname -r returns 12.1-p2. I then atempted to upgrade
installed-jail ports and got this message:

/!\ ERROR: /!\

Ports Collection support for your FreeBSD version has ended, and no ports are
guaranteed to build on this system. Please upgrade to a supported release.

No support will be provided if you silence this message by defining
ALLOW_UNSUPPORTED_SYSTEM.

I'd appreciate any pointers.
Thanks.
Dave.