ZFS chroot cannot open dev nodes

[Roy Marples <roy%marples.name@localhost>]

I'm experimenting with ZFS on a new server.
Trying to get root on ZFS, but it's not working with device nodes.

Here are exact steps from the real root on FFS.
There is a zfs mount on /tank/ROOT.

# cd /tmp
# mknod null c 2 2
# echo test >null
# cd /tank/ROOT/tmp
# mknod null c 2 2
# echo test >null
-sh: cannot create null: error 22

Any clue as to why?
zfs gets devices shows that every mount has it set to on and mount does not 
report the nodev option, so it *should* work.

What am I missing? Does anyone else see this?

This is NetBSD-9.0_RC2 if that helps.

Roy