plpgsql overloading bug in 7.3.2 on OS X

I'm having trouble overloading functions in plpgsql using PostgreSQL
7.3.2 on OS X.

I have created two functions with the following declarations:

CREATE OR REPLACE FUNCTION set_entity_type(BIGINT,TEXT) RETURNS BOOLEAN
AS ' ...
CREATE OR REPLACE FUNCTION set_entity_type(BIGINT,BIGINT) RETURNS
BOOLEAN AS ' ...