A local replication entry

I think maybe it's just too early in the morning for me, but I can't seem to get a local entry for replication working.
I'mtrying to create a script for hourly backups using  
pg_basebackup, and here's the command I'm using:

/usr/pgsql-9.3/bin/pg_basebackup -D - -Ft -z -c fast -l hourly.backup > backup_file.gz

The entry in the pg_hba.conf file is:

local    replication    postgres                            trust

And the error is: FATAL: no pg_hba.conf entry for replication connection from host "[local]", user "postgres", SSL off,
butI have gotten this to work only if I use a "-h  
10.10.1.129" option for the command. This only works since another entry in the pg_hba.conf satisfies the command.

Do I have an error with the local entry? Or are local entries even allowed for replication? As this has to be
automaticallydeployed to various servers, I'd prefer to NOT specify  
each host's IP address both in pg_hba.conf file and in the script calling the pg_basebackup command. Oh, and at some
pointwhen this starts working, I am going to change the user  
from postgres to another without superuser capability.
--
Jay