Widget with Qt::FramelessWindowHint flag is not minimized

1. Create widget with Qt::FramelessWindowHint flag.

Widget::Widget(QWidget *parent)
: QWidget(parent,Qt::FramelessWindowHint)
{
}

2. Run program.
3. Click on the application icon in the taskbar.
4. Application is NOT minimized.

If add button and call QWidget::showMinimized() - widget minimized normal.