showMinimized() doesn't work when using FramelessWindowHint on Mac

#include <QApplication>
#include <QPushButton>

class MyWidget : public QWidget
{
	Q_OBJECT
public:
	MyWidget() : QWidget(),minButton("minimize",this) {
		setWindowFlags(
				Qt::Window
				|Qt::FramelessWindowHint
				|Qt::WindowSystemMenuHint
				|Qt::WindowMinimizeButtonHint
				|Qt::WindowMaximizeButtonHint
				);
		connect(&minButton,SIGNAL(clicked()),this,SLOT(minimize()));

	}
public Q_SLOTS:
	void minimize() {
		showMinimized();
	}
private:
	QPushButton minButton;
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
	MyWidget w;
	w.show();
    return a.exec();
}
#include "main.moc"