[Lazarus] Missing (compatible) underlying dataset, can not open

["Leonardo M. Ramé"]

Hi, I'm trying to execute this query, but I'm getting "Missing 
(compatible) underlying dataset, can not open".

lQuery.DataBase := PQConnection1;
lQuery.ParseSQL:= false;
lQuery.SQL.Text:= 'select json_agg(resultset) as json from(select 1) as 
resultset';
lQuery.Open;

The query runs without problems in PostgreSql 9.3 both from pgAdmin and 
psql.

Any hint?.

-- 
Leonardo M. Ramé
Medical IT - Griensu S.A.
Av. Colón 636 - Piso 8 Of. A
X5000EPT -- Córdoba
Tel.: +54(351)4246924 +54(351)4247788 +54(351)4247979 int. 19
Cel.: +54 9 (011) 40871877