zfs process dumps core in 12.0-BETA w/ jail zfs datasets

The zfs process core dumps, apparently related to iocage attempting to assign a dataset to a jail.

Backtrace -
Core was generated by `zfs jail ioc-pgsql zedpm/postgresql'.
Program terminated with signal SIGABRT, Aborted.
#0  0x00000008008fb9ca in thr_kill () from /lib/libc.so.7
(gdb) where
#0  0x00000008008fb9ca in thr_kill () from /lib/libc.so.7
#1  0x00000008008f9e34 in raise () from /lib/libc.so.7
#2  0x00000008008700d9 in abort () from /lib/libc.so.7
#3  0x00000008002e6281 in zfs_standard_error_fmt () from /usr/local/lib/libzfs.so.4
#4  0x00000008002e5db5 in zfs_standard_error () from /usr/local/lib/libzfs.so.4
#5  0x00000008002e9ca8 in zfs_jail () from /usr/local/lib/libzfs.so.4
#6  0x000000000021bd8e in ?? ()
#7  0x000000000020e712 in ?? ()
#8  0x000000000020d650 in ?? ()
#9  0x000000080024b000 in ?? ()
#10 0x0000000000000000 in ?? ()

Trying to run that zfs command manually:

freenas# zfs jail 2 zedpm/postgresql
internal error: Inappropriate ioctl for device
Abort trap

The running version is 12.0-BETA - I can't find anything more specific on the machine but it's the currently available version as of a few hours ago.