xtrabackup tmpdir

Hi

I am using innobackupex to run a backup, but need to specify tmpdir for xtrabackup (as my /var/tmp/ is only 10GB, and runs out of space during the backup)

innobackupex has a --tmpdir option, but that does not seem to be passed to xtrabackup.

Is there any way to specify the xtrabackup --tmpdir option when using innobackupex?

Thanks