MonthGrid: QQmlContext: Cannot set property on internal context.

import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.0
import Qt.labs.calendar 1.0

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    GridLayout {
        columns: 2

        DayOfWeekRow {
            locale: grid.locale

            Layout.column: 1
            Layout.fillWidth: true
        }

        WeekNumberColumn {
            month: grid.month
            year: grid.year
            locale: grid.locale

            Layout.fillHeight: true
        }

        MonthGrid {
            id: grid
            month: Calendar.December
            year: 2015
            locale: Qt.locale("en_US")

            Layout.fillWidth: true
            Layout.fillHeight: true
        }
    }
}