When assigning a QQmlListProperty of QObjects that are Javascript owned to a variable inside QML then it is not garbage collected when there are no references to it anymore. Therefore it is leaking this as it is not reclaimed even when the application is closed down either. In the example, the commented out approach which assigns the object in the list directly shows that it works that way, but the approach used where it assigns the whole list is not cleaned up, even though there are no more references to it.