sp: error message not coherent with actual code

I've this line in a sp:

select into _OrderGroupID b2c._OrderGroupID from
Basket2Order(_BasketID) as b2c;

but I get this error:

SELECT query has no destination for result data HINT: If you want to
discard the results, use PERFORM instead. CONTEXT: PL/pgSQL function
"basket2order" line 71 at SQL statement SQL statement "SELECT
b2c._OrderGroupID from Basket2Order( $1 ) as b2c"

?

Commenting that line the error goes away.

--
Ivan Sergio Borgonovo
http://www.webthatworks.it