Popup's contentItem isn't mirrored if no Window exists

import QtQuick 2.7
import QtQuick.Layouts 1.3
import QtQuick.Controls 2.3
import QtQuick.Window 2.2

Item { //with Window the RowLayout in myPopup order is reversed (mirroring is applied)
    LayoutMirroring.enabled: true
    LayoutMirroring.childrenInherit: true

    width: 350
    height: 150

    RowLayout {
        anchors.fill: parent
        Button {text: "1"}
        Button {
            text: "2 clickable"
            onClicked: {
                myPopup.open()
                console.log(myPopup.contentItem.LayoutMirroring.enabled)
            }
        }
    }

    Popup {
        id: myPopup
        Component.onCompleted: {
            console.log("completed")
            console.log(contentItem.LayoutMirroring.enabled)
        }
        RowLayout {
            anchors.fill: parent
            Button {text: "1"}
            Button {text: "2"}
        }
    }
}