SQLSTATE exception thrown from exception handling block prevents plpgsql function from compiling

PostgreSQL 9.0 Beta2, Windows XP Professional SP2.

The following function doesn't seem to compile in PostgreSQL 9.0 while 8.4 accepts it with no problem.

CREATE OR REPLACE FUNCTION test.delete_sessions()
RETURNS void AS
$BODY$
BEGIN
select 1;
EXCEPTION WHEN SQLSTATE '55P03' THEN
RAISE SQLSTATE '55P03' using MESSAGE ='test message';
END
$BODY$
LANGUAGE 'plpgsql' VOLATILE
COST 100;