Strange behaviour with Q_OBJECT_BINDABLE_PROPERTY and std::unique_ptr

class Foo : public QObject
{
    Q_OBJECT
    Q_PROPERTY(int x READ x WRITE setX NOTIFY xChanged BINDABLE bindableX)
    Q_PROPERTY(int * p READ getP  NOTIFY pChanged BINDABLE bindableP)
public:
    explicit Foo(QObject *parent = nullptr);

    int x() const { return xProp; }
    void setX(int x) { xProp = x; emit xChanged();}
    QBindable<int> bindableX() { return QBindable<int>(&xProp); }

    int * getP() const { return p.value().get(); }
    void setP(std::unique_ptr<int> x) { p = std::move(x); emit pChanged();}
    QBindable<const std::unique_ptr<int>&> bindableP() { return QBindable<const std::unique_ptr<int>&>(&xProp); }

signals:
    void xChanged();
    void pChanged();

private:
    Q_OBJECT_BINDABLE_PROPERTY(Foo, int, xProp, &Foo::xChanged)
    Q_OBJECT_BINDABLE_PROPERTY(Foo, std::unique_ptr<int>, p, &Foo::pChanged)
};

int main(int argc, char *argv[])
{
    Foo f;
    auto b = f.bindableP().subscribe([&]{
        qDebug() << "pointer changed to" <<f.getP() ;
    });
    auto b2 = f.bindableX().subscribe([&]{
        qDebug() << "x changed to" <<f.x() ;
    });
    QProperty<int> test;
    test.setBinding([&]{
        auto p =f.getP();
        if(p)
            return *p * 2;
        return -1;
    });
    auto ts = test.subscribe([&](){qDebug() << "test is now" << test;});
    f.setP(std::make_unique<int>(20));
    f.setX(4);
    qDebug() << "test";
    f.setP(std::make_unique<int>(30));
    f.setX(5);
    qDebug() << "test";
    return 0;
}