plpgsql Difference in behaviour between versions?

Hi,
I am upgrading a system from postgresql 8.4.8 (fedora 13 x64) to postgresql 9.0.5 (fedora 15 x64). As I build a
databaseI've noticed that the following works on 8.4.8 but does not work on 9.0.5. Can someone tell me why this is not
legalsyntax in 9.0.5 but is legal in 8.4.8 please: 

===snip===
create type mytype
as
(
   somekey integer,
   open numeric(14, 2)
);

CREATE OR REPLACE FUNCTION myfunc(IN INTEGER, IN NUMERIC(14, 2))
    RETURNS VOID
AS $$
DECLARE
    somekey ALIAS FOR $1;
    rec mytype;
BEGIN
    rec.somekey = somekey;

        -- 9.0.5 will fail at the dot character in the
        -- following line here with syntax error sqlstate 42601
        -- but 8.4.8 is happy.
    rec.open = 32;
        -- ^

    RETURN;
END;
$$ LANGUAGE plpgsql;
===snip===