"TypeError: Cannot read property 'x' of undefined" when binding to delegate index and model role in the same binding

import QtQuick 2.0
import QtQuick.Controls 2.0

import Isle 1.0

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

    Flow {
        Repeater {
            id: pathRepeater
            model: PathModel {
                id: pathModel
            }
            delegate: Label {
                // Works fine
//                text: model.tilePos.toString()
                // TypeError: Cannot read property 'x' of undefined
                // Works if you comment out "index" in the last expression in parentheses.
                text: "(" + model.tilePos.x + ", " + model.tilePos.y + ")" + (index < pathRepeater.count - 1 ? " " : "")
            }
        }
    }

    Button {
        text: "Remove first path node"
        anchors.bottom: parent.bottom

        onClicked: pathModel.removeFirst()
    }
}

    required property int index
    required property var model

    text: "(" + tilePos.x + ", " + tilePos.y + ")" + (index < pathRepeater.count - 1 ? " " : "")
    
    required property int index
    required property point tilePos