Adding Default Privileges to a schema for a role

Hello,

I created a role called Workers. I am able edit the privileges for the Workers role in the public schema of a database. I also would like to edit the default privileges of the schema as well so that the Workers group will automatically have read permissions to any tables created in the future. In pgAdmin III I opened up the Default privileges for the public schema and I only see the Public role in the Role/ Group dropdown. Is there any reason why I can see other groups in the Privileges tab, but not the Default Privileges tab?

P.S. I did notice on an older (9.0?) 32 bit version of PostGIS I am able to see more than just the public role in the Default Privileges tab. I don't remember doing anything special to see other groups on the older machine. This isn't a bug is it?

Thank You

Mark Volz
GIS Specialist