Qt Quick Controls 2 Button fails creation in GridView

import QtQuick 2.6
import Qt.labs.controls 1.0
ApplicationWindow {
    visible: true
    width: 640
    height: 480

    GridView {
        id: gridThing;
        anchors.fill: parent;
        cellWidth: 75;
        cellHeight: 75;
        model: 500;

        delegate: Button {
            id: control
            text: "Test"
            width: gridThing.cellWidth;
            height: gridThing.cellHeight;
            background: Rectangle {
                implicitHeight: 20;
                implicitWidth: 20;
                color: "red";
                width: control.width;
                height: control.height;
                x: 0;
                y: 0;
            }
        }
    }
}