Error in select

Hello.

When I run the next query:

SELECT DATE_TRUNC('hour', TL.TAL005_DATE), TL.SRV_ID, TL.MSU_NUMBER,
       DS.DESCRIPTION, DS.CALLTYPE, COUNT(*)
FROM   OWNER_CATALOG.TAL005 TL,
       OWNER_CATALOG.DS_AREA_CODE DS
WHERE  SRV_ID      = 1                  AND
       TAL005_DATE > to_date('01011900','ddmmyyyy')               AND
       DS.CODE     = ( SELECT MAX(DSS.CODE)
                       FROM   OWNER_CATALOG.DS_AREA_CODE DSS
                       WHERE  DSS.CODE =
SUBSTR(TL.TAL005_INCLI,1,LENGTH(DSS.CODE)))
GROUP  BY DATE_TRUNC('hour', TL.TAL005_DATE), TL.SRV_ID, TL.MSU_NUMBER,
DS.DESCRIPTION,DS.CALLTYPE;

I get:

ERROR:  variable not found in subplan target list

This query works fine in 7.3.4, but we are migrating to 7.4 and it
doesn't work.

Some idea about the problem????

Thanks.

CG