13.4 and zfs.mount_snapshot for jail

Hello.

I've been using ezjail with:
> export jail_fs_parameters="allow.mount.fdescfs=true enforce_statfs=1 zfs.mount_snapshot=1"
for a long time.
It works on 13.3 and 14.1.

However, I upgraded one machine to 13.4 and now such a jail does not 
start anymore:
> # ezjail-admin start fs
> Starting jails: cannot start jail  "fs2": 
> jail: fs: jail_set: Invalid argument
> .
> /etc/rc.d/jail: WARNING: Per-jail configuration via jail_* variables  is obsolete.  Please consider migrating to /etc/jail.conf.
> Error: Could not restart fs.
>   You need to restart it by hand.

I searched UPDATING, docs, bugs, etc... but could not find anything 
relevant.
Is this a regression or does the config need some change in any way?

  bye & Thanks
	av.