Mac: Qt::Sheet dialog permanently loses focus after moving the parent window

#include <QtGui>

class Dialog : public QDialog
{
public:
  Dialog(QWidget *parent=0);
};

Dialog::Dialog(QWidget* parent) : QDialog(parent)
{
  setWindowMoXXXXty(Qt::WindowModal);
  setWindowFlags((windowFlags() & ~Qt::WindowType_Mask) | Qt::Sheet);

   QGridLayout* grid = new QGridLayout(this);
   grid->addWidget(new QLineEdit("Click Me"), 0,0);
   grid->addWidget(new QLabel("Click insite the QLineEdit - it should get a blue border (focused). \n\n"
                              "Now click the parent window's header, for example to move it. \n\n"
                              "Now click the QLineEdit again - it does not get the blue border anymore. \n"
                              "You can type inside, but it looks like inactive. \n\n"
                              "The same will happen to all widgets in the dialog - they will be greyed out, \n"
                              "like they do not receive the focus anymore."), 1,0);
   QPushButton *btnClose = new QPushButton("Close");
   connect(btnClose, SIGNAL(clicked()), this, SLOT(close()));
   grid->addWidget(btnClose, 2,0);
}

int main(int argc, char **argv)
{
  QApplication app(argc, argv);

  QWidget w;
  Dialog* d = new Dialog(&w);
  w.show();
  d->show();

  return app.exec();
}