pg_ctl of postgres 8.4 doesn't behave the same than 9.x when using a custom unix socket path

*In brief*
I think there is an issue with *pg_ctl of PostgreSQL 8.4*, it doesn't
behave the same than 9.1 and 9.3 (didn't tested 9.2 yet). It does not give
me back the control if I use *a unix socket different than /run/postgresql
and disable listening*.

*Details*
I'm running a Gentoo and try make multiple version of PostgreSQL running on
the same system.

Instead of changing port, I prefer to disable the listening on an interface
and use only a unix socket with a meaningful directory.

Here are the changes I made in the postgresql.conf file:

> listen_addresses = ''
> unix_socket_directory = '/run/postgresql-8.4'
>

Then I run:

> . /etc/conf.d/postgresql-8.4
>

(to load the configuration variable of Gentoo in my current shell)

> su -c "pg_ctl84 start -D ${DATA_DIR} -s -l ${DATA_DIR}/postmaster.log -o
> \"-p ${PGPORT} -D ${PGDATA} --data-directory=${DATA_DIR}\" -w -t 300" po
> stgres
>

Here are the log in ${DATA_DIR}/postmaster.log:

LOG: database system was shut down at 2014-05-07 02:56:22 CEST
> LOG: database system is ready to accept connections
> LOG: autovacuum launcher started
> LOG: received smart shutdown request
> LOG: autovacuum launcher shutting down
> LOG: shutting down
> LOG: database system is shut down
> LOG: database system was shut down at 2014-05-07 03:01:31 CEST
> LOG: autovacuum launcher started
>

*The problem is*
The program never gives back the control to the parent process but the
server is actually running normally.* This is not the same behavior in 9.1
and 9.3.* I get the control back in less than a second after I run the
pg_ctl process.

It makes my system.d service stuck in "activating" state.

Here is system.d the status of the service:

> postgresql-8.4.service - PostgreSQL database server
> Loaded: loaded (/usr/lib64/systemd/system/postgresql-8.4.service;
> enabled)
> Active: activating (start) since Wed 2014-05-07 03:30:25 CEST; 45s ago
> Process: 1041 ExecStartPre=/usr/bin/postgresql-8.4-check-db-dir
> (code=exited, status=0/SUCCESS)
> Main PID: 5437 (code=exited, status=1/FAILURE); : 1044 (pg_ctl)
> CGroup: /system.slice/postgresql-8.4.service
> ├─1044 /usr/lib/postgresql-8.4/bin/pg_ctl start -D
> /var/lib/postgresql/8.4/data -s -l
> /var/lib/postgresql/8.4/data/postmaster.log -o -p 5432 -D /e...
> ├─1047 /usr/lib64/postgresql-8.4/bin/postgres -D
> /var/lib/postgresql/8.4/data -p 5432 -D /etc/postgresql-8.4
> --data-directory=/var/lib/postgresql/...
> ├─1049 postgres: writer process
> ├─1050 postgres: wal writer process
> ├─1051 postgres: autovacuum launcher process
> └─1052 postgres: stats collector process
>

*This problem does not occur if I use the default unix socket path
/run/postgresql*

Best regards