Bug with FOR ... LOOP and composite types

Hello.

Seems there is an error when I try to use a table with one field - composite
type, when SELECT QUERY in FOR ... LOOP instruction returns empty result.
Here are steps to reproduce:

CREATE TYPE "t_type" AS (
"a" BIGINT
);

CREATE TABLE"t_table" (
"id" BIGINT NOT NULL,
"t" "t_type",
CONSTRAINT "t_table_pkey" PRIMARY KEY("id")
) WITH OIDS;

CREATE OR REPLACE FUNCTION "t_func" () RETURNS SETOF "t_table" AS
$body$
DECLARE
rec t_table%ROWTYPE;
BEGIN
FOR rec IN
SELECT *
FROM t_table
WHERE 1=0
LOOP
RETURN NEXT rec;
END LOOP;
END;
$body$
LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY INVOKER;

SELECT * FROM t_func()

Result:

ERROR: cannot assign non-composite value to a row variable
CONTEXT: PL/pgSQL function "t_func" line 4 at FOR over SELECT rows