On Qt Carbon, the flag Qt::FramelessWindowHint is ignored for modal window with a title

Here is an example to reproduce the problem (the title bar is shown, even with FramelessWindowHint):

#include <QtGui>

int main(int argc, char **argv){
QApplication app(argc, argv);
QDialog widget;
widget.setWindowTitle("QtSoftware");
widget.setWindowFlags(Qt::FramelessWindowHint);
widget.setModal(true);
widget.show();
return app.exec();
}