MapPolygon with 2 points not drawn if using mapboxgl plugin

import QtQuick 2.8
import QtQuick.Window 2.2
import QtPositioning 5.8
import QtLocation 5.9

Window {
    visible: true
    width: 640
    height: 480

    Map {
        id: theMap

        anchors.fill: parent
        plugin: Plugin {
//            name: "osm"
            name: "mapboxgl"
//            PluginParameter { name: "mapboxgl.mapping.use_fbo";             value: "false"  }
//            PluginParameter { name: "mapboxgl.mapping.items.insert_before"; value: "false"  }
        }
        center: QtPositioning.coordinate(60,10);

        Timer {
            property double counter: 0

            interval: 16
            repeat: true
            running: true
            triggeredOnStart: true
            onTriggered: {
                counter = counter + 0.01;
                var path = thePolygon.path;
                path[1] = QtPositioning.coordinate(60.0+Math.sin(counter), 10.0+Math.cos(counter));
                thePolygon.path = path
                theMap.center = path[1];
            }
        }

        MapPolygon {
            id: thePolygon
            path: [
                { latitude: 60,   longitude: 10 },
                { latitude: 60.5, longitude: 10 },
            ]
            color: "#11223344"
            border.color: "blue"
            border.width: 2
        }
    }
}