QTooltip do not appear to screen on Symbian

Tooltip does not appear to screen with following code:

#include <QTooltip>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
test w;
w.show();
QString string("tool tip");
QPoint pos(100,160);
QToolTip::showText(pos,string);
return a.exec();
}

Also tried to set tooltip to QPushButton but it wont either appear.

Tested with N97 sdk Qt 4.6.2