QML Settings object has no sync()

import QtQuick 2.12
import QtQuick.Window 2.12
import Qt.labs.settings 1.0
Window {
    id: window
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World") 
    onWidthChanged: wh.sync()
    Settings {
        id: wh
        property alias w: window.width
        property alias h: window.height
        Component.onCompleted: wh.sync()
        onWChanged: sync()
    }
}

qrc:/main.qml:20: ReferenceError: sync is not defined
qrc:/main.qml:12: TypeError: Property 'sync' of object QQmlSettings_QML_0(0x2379a70) is not a function
qrc:/main.qml:19: TypeError: Property 'sync' of object QQmlSettings_QML_0(0x2379a70) is not a function