ExecSQL (no replies)

Why do I get a 'can't perform operation on a closed dataset' error on the following code?????

qRptStuff2 := TFDQuery.Create( AConnection );
with qRptStuff2 do
begin
Connection := AConnection;
SQL.Add( 'Insert into RptStuff2 (DateA,IntA,FloatA,StrA) values (:D,:I,:R,:DD)' );
ParamByName('D').AsDate := dDate;
ParamByName('I').AsInteger := InvDay;
ParamByName('R').AsFloat := RevDay;
ParamByName('DD').AsString := DateToStr( dDate );
ExecSQL;