polymorphic function in 7.4 vs. 8.3

I have the following setup which works great in version 8.3 but throws an
error in 7.4:

CREATE TABLE atest1
(
id integer NOT NULL,
descr text,
CONSTRAINT atest1_pkey PRIMARY KEY (id)
);

CREATE OR REPLACE FUNCTION test_trg()
RETURNS "trigger" AS
'
DECLARE
any_rec wfsys.atest1;

BEGIN
any_rec.id := NEW.id;
any_rec.descr := NEW.descr;
select into any_rec * from dd_test(any_rec);
--any_rec := dd_test(any_rec);
RETURN any_rec;
END;
'
LANGUAGE 'plpgsql' VOLATILE;

CREATE OR REPLACE FUNCTION dd_test(anyelement)
RETURNS record AS
'
DECLARE
any_rec alias for $1;
some_row record;
BEGIN
some_row := any_rec;
if some_row.id < 0 then
raise notice ''id is < 0!'';
some_row.descr := ''some other value'';
end if;
RETURN some_row;
END;
'
LANGUAGE 'plpgsql' VOLATILE;

CREATE TRIGGER trg_atest1
BEFORE INSERT
ON atest1
FOR EACH ROW
EXECUTE PROCEDURE test_trg();

Finally, firing the trigger like so:

insert into wfsys.atest1 values(123, 'some text');

Gives the following error:

ERROR: column "any_rec" does not exist
CONTEXT: PL/pgSQL function "test_trg" line 7 at select into variables

********** Error **********

ERROR: column "any_rec" does not exist
SQL state: 42703
Context: PL/pgSQL function "test_trg" line 7 at select into variables

It works great on 8.3 (my dev server), but throws the error on the machine I
am forced to work with, which is running version 7.4. I realize that
polymorphic functions were pretty new in v7.4, is there a workaround or am I
making a silly mistake? Or both?

Incidentally, I get the same error when I change the polymorphic function's
argument from "anyelement" to "wfsys.atest1" so it seems that it is occurring
in the trigger function. Thanks for any help.

Richard