does numeric only name of jails not allowed (bug?)

Dear freebsd-hackers.

It seems there is no sign that numeric only name is prohibited:

"
The jail name.  This is an arbitrary string that identifies a
             jail (except it may not contain a �.�).
"

But 
# head jail-47777.conf
...
47777 {
        host.hostname = "${name}";
...

# jail -c 47777
jail: 47777: host.hostname: variable "name" not found

If I add letter prefix, say w47777, it worked.

Because of strange error "variable "name" not found" it seems like a bug. Does it?


-- 
Best regards,
 Anthony                          mailto:anthony.pankov@yahoo.com