Numeric type in PL/pgSQL trigger: overflow problem

Hi,

 following function doesn't work with numeric type, when I change type
of 'total_no_vat' to anything else incl. float it works OK. What am I
doing wrong? Thanks for your help.

- Robert

CREATE TABLE deb_invoice_line_table (
		qty		NUMERIC(13,2),
		unit_price	NUMERIC(13,2),
		total_no_vat	NUMERIC(13,2),
		-- ...
)

CREATE FUNCTION deb_invoice_line_complete() RETURNS OPAQUE AS 'BEGIN
	NEW.total_no_vat := 5.2;
	RETURN NEW;
END;' LANGUAGE 'plpgsql';

CREATE TRIGGER deb_invoice_line_trigger
	BEFORE INSERT OR UPDATE
	ON deb_invoice_line_table
	FOR EACH ROW EXECUTE PROCEDURE deb_invoice_line_complete();

INSERT INTO deb_invoice_line_table (qty,unit_price) VALUES (3,33);

ERROR:  overflow on numeric ABS(value) >= 10^0 for field with precision
0 scale 2