Can't set property change handler on bindable properties without setter

class Foo : public QObject {
    Q_OBJECT
    QML_ELEMENT
    Q_PROPERTY(int count READ count BINDABLE countBindable)
public:
    int count() const { return mCount; }
    QBindable<int> countBindable() { return &mCount; }

private:
    Q_OBJECT_BINDABLE_PROPERTY(Foo, int, mCount, nullptr)
};

Foo {
    onCountChanged: console.info("count changed")
}

qrc:/main.qml:50:25: Invalid property assignment: "count" is a read-only property