QEasingCurve streaming operators (in/out a QDataStream) will crash

QDataStream &operator<<(QDataStream &stream, const QEasingCurve &easing)
{
    stream << quint8(easing.d_ptr->type);
    stream << quint64(quintptr(easing.d_ptr->func)); // <-- HERE

    bool hasConfig = easing.d_ptr->config;
    stream << hasConfig;
    if (hasConfig) {
        stream << easing.d_ptr->config;
    }
    return stream;
}

QDataStream &operator>>(QDataStream &stream, QEasingCurve &easing)
{
    QEasingCurve::Type type;
    quint8 int_type;
    stream >> int_type;
    type = static_cast<QEasingCurve::Type>(int_type);
    easing.setType(type);

    quint64 ptr_func;
    stream >> ptr_func;
    easing.d_ptr->func = QEasingCurve::EasingFunction(quintptr(ptr_func)); // <-- HERE

    bool hasConfig;
    stream >> hasConfig;
    delete easing.d_ptr->config;
    easing.d_ptr->config = nullptr;
    if (hasConfig) {
        QEasingCurveFunction *config = curveToFunctionObject(type);
        stream >> config;
        easing.d_ptr->config = config;
    }
    return stream;
}