Problem with return type of function ??? (corrected)

Hello, (CORRECTED VERSION OF MY PREVIOUS EMAIL)

I have a strange problem, because it worked in a fonction for a table,
and now I created the same (?) function for another table and it doesn't
work...

The function is accepted but at runtime I get :

ERREUR: wrong record type supplied in RETURN NEXT
CONTEXTE : PL/pgSQL function "find_sn_live" line 26 at return next

Does someone maybe knows what it could be ?

This is (a part of) my function :

> CREATE OR REPLACE FUNCTION rma.find_sn_live (varchar(30)) RETURNS SETOF rma.serial_number
> AS $_$
> DECLARE
> serialnumber ALIAS FOR $1;
> row RECORD;
> BEGIN
>
> FOR row IN
> SELECT * FROM rma.serial_number WHERE sn=serialnumber
> LOOP
> RETURN NEXT row;
> END LOOP;
>
> END;
> $_$
> LANGUAGE plpgsql STRICT;

Thanks a lot for any help !

Denis