QPolygonF::subtract returns wrong polygon

#include <QPolygonF>
#include <QRectF>
#include <QDebug>

int main()
{
    QPolygonF   poly1(QRectF(0, 2, 1, 2));
    QPolygonF   poly2(QRectF(0, 0, 1, 4));

    qDebug() << "poly1 = " << poly1;
    qDebug() << "poly2 = " << poly2;
    qDebug() << "poly2.subtracted(poly1) = " << poly2.subtracted(poly1);

    // Reported result should be:
    // QPolygonF(QPointF(0,0), QPointF(1,0), QPointF(1,2), QPointF(0,2), QPointF(0,0));
   // but is
   // QPolygonF(QPointF(0,2)QPointF(1,2)QPointF(1,4)QPointF(0,4)QPointF(0,2)QPointF(0,0)QPointF(1,0)QPointF(1,4)QPointF(0,4)QPointF(0,0)QPointF(0,2))
}