Install htop in FreeBSD

make install in /usr/ports/sysutils/htop will get an error message :

***********************************************************
htop(1) requires linprocfs(5) to be mounted. If you don't
have it mounted already, please add this line to /etc/fstab
and run `mount linproc`:
linproc /compat/linux/proc linprocfs rw 0 0
***********************************************************

By message :

$ echo "linproc /compat/linux/proc linprocfs rw 0 0" >> /etc/fstab
$ mount linproc

Then make install again.