MenuItem mnemonic shortcut not triggered

import QtQuick
import QtQuick.Controls
import Qt.labs.platform as Platform

ApplicationWindow {
    id: window
    width: 640
    height: 480
    visible: true
 
    menuBar: MenuBar {
        property Platform.FileDialog fileDialog
        
        Menu {
            id: fileMenu
            title: qsTr("&File")
            
            MenuItem {
                objectName: "openMenuItem"
                text: qsTr("Open")
                onTriggered: fileDialog.open()
            }
            
            MenuSeparator {}
            
            MenuItem {
                objectName: "quitMenuItem"
                text: qsTr("E&xit")
                onTriggered: Qt.quit()
            }
        }
    }
}