Get diagnistic (row_count) 7.3 vs. 7.4 changes

Hi,
Just trying 7.4.5 and bumped into a problem.

consider following code:

CREATE OR REPLACE FUNCTION rowcount_test() RETURNS bigint AS '
DECLARE
base_hits bigint;
BEGIN
CREATE TEMP TABLE ltbl_temp AS SELECT 1 AS data;
GET DIAGNOSTICS base_hits = ROW_COUNT;

RETURN base_hits;
END;
' LANGUAGE PLPGSQL VOLATILE;

in 7.3.3 GET DIAGNOSTICS was returning number of selected rows into a temp
table
in 7.4.5 GET DIAGNOSTICS returns 0

Is it known behavior change or something else.
Thank you.