Crash when accessing enums defined in QML_SINGLETON class

#include <QObject>
#include <QQmlEngine>

class DummyObjekt : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    QML_SINGLETON // This causes the crash

public:
    enum Test {
        TestA = 1,
        TestB
    };
    Q_ENUM(Test)

public:
    explicit DummyObjekt(QObject *parent);
};

import QtQuick 2.15
import QtQuick.Controls.Material 2.0
import QtQuick.Layouts 1.3

import com.test

ApplicationWindow {
    id: window
    width: 640
    height: 480
    visible: true
    title: qsTr("Test")

    Button {
        id: btn
        text: "Click me"
        onClicked: {
            console.log("Dummy: " + DummyObjekt.TestA); // Crash
        }
    }
}