pgbouncer not finding pidfile

Hi,

I am trying to start pgbouncer via upstart script. The upstart logs
(/var/log/upstart/pgbouncer.log) tell me:
/var/run/postgresql/pgbouncer.pid: No such file or directory [2]

but when starting pgbouncer from the console with:

> sudo service pgbouncer start

it works fine and the pidfile is created.

Here is the upstart script (/etc/init/pgbouncer.conf):

start on (net-device-up and local-filesystems and runlevel [2345])
stop on runlevel [016]

setuid postgres
setgid postgres
respawn limit 10 30

exec /usr/sbin/pgbouncer /etc/pgbouncer/pgbouncer.ini

The permissions for the folder seem ok:

> ls -lsah /var/run/ | grep postgresql
0 drwxrwsr-x 2 postgres postgres 100 Jul 29 04:18 postgresql

I have no clue whats wrong.
Any help would be appreciated.
Tobi