Why can't I boot a non-global zone that has an LOFS fs resource mounted under /var?

I'm running Sol 11.1 SRU 20.5. I configured a basic zone, with the following "fs" resource:

add fs
set dir=/var/subversion
set special=/var/subversion
set type=lofs
end

In the global zone, the mountpoint for the pool1/var/subversion ZFS filesystem is /var/subversion, and it's mounted and available.

However, when I attempt to boot the non-global zone named "dev-web", I get the following errors:

root@<server>:~# zoneadm -z dev-web boot
zone 'dev-web': WARNING: net0: no matching subnet found in netmasks(4): <IP>; using default of 255.255.255.0.
zone 'dev-web': cannot unmount '/zones/dev-web/root/var': Device busy
zone 'dev-web': ERROR: unable to unmount /zones/dev-web/root/var.