QPSQL reports an error when executing a query.

When having the prepared QSqlQuery below for a postgresql 8.3.6 database.

insert into user_records (service_number,event_number,stop_time) values (?,?,timestamp ? + time ?)

then QPSQL always reports an error when executing this query:

ERROR: syntax error at or near "("
LINE 1: EXECUTE (93, 37, '2009-8-14 19:30:00.000', '02:00:00')
^
QPSQL: Unable to create query

However, when executing the query in the postgresql client it succeeds!

client query:
insert into user_records (service_number,event_number,stop_time) values (93,37,timestamp '2009-8-14 19:30:00.000' + time '02:00:00');