Qt Platform Menu QML Type cannot create sub menus on Windows

import QtQuick 2.6
import QtQuick.Window 2.2
import Qt.labs.platform 1.0

Window {
    width: 300
    height: 300
    visible: true

    MouseArea {
        anchors.fill: parent
        acceptedButtons: Qt.RightButton
        onClicked: menu.open()
    }

    Menu {
        id: menu
        Menu {
            title: qsTr ("Sub Menu 1")
            MenuItem {
                text: "Sub Menu 1 Item"
            }
        }
        Menu {
            title: qsTr ("Sub Menu 2")
            MenuItem {
                text: "Sub Menu 2 Item"
            }
        }
    }
}