Equiv /etc/fstab entry for mount -n

[will3477]

Basically I need to use mount with the -n option (tells it not to modify /etc/mtab). If I use
mount -t shfs -n server:/directory /mnt/tmp

Then everything works fine. What I don't know how to do is when I make an entry in /etc/fstab, how do I tell it not to touch /etc/mtab (the equivalent of the -n flag).

Its so basic that it was hard to form google queries, but I'll happily RTFM if you can point me to the right M

Thanks,
Bill