DropShadow won't work on piled window on Windows 7 which is using Intel GPU

Window {
    visible: true
    width: 640
    height: 480
    flags: Qt.Window |
           Qt.FramelessWindowHint

    Rectangle {
        anchors.fill: parent
        color: "blue"
    }

    Window {
        id: win
        visible: true
        width: 320 + (60 * 2)
        height: 240 + (60 * 2)
        color: "transparent"
        modality: Qt.ApplicationModal
        flags: Qt.Window |
               Qt.FramelessWindowHint

        Rectangle {
            id: rect
            anchors.fill: parent
            anchors.margins: 60
            color: "blue"

            layer.enabled: true
            layer.effect: DropShadow {
                anchors.fill: rect
                source: rect
                horizontalOffset: 1
                verticalOffset: 1
                radius: 40
                samples: 40
                color: '#aa000000'
            }
        }
    }
}