[Exim] "-oP" option not working

Set up fresh install of Exim version 4.22 #1 on FreeBSD 4.9-RELEASE box (also
new install).

Start second instance of exim (with separate configuration file and spool
directory) with following script:

[code]
#!/bin/sh
#
/usr/local/sbin/exim -bd -q15m \
-oX 2500 \
-oP /var/run/exim.[second instance].pid \
-C /usr/local/etc/exim/exim.conf.[second instance]
#
exit
[end of code]

It works fine, except that the pid file for the second instance does not get
written.

Have tried "-oP /var/spool/exim.[second instance]/exim.pid"

and "-oP /var/spool/exim.[second instance]/exim.[second instance].pid"

with no joy.

Any ideas?

Thank you.

Jack