QFuture::onCanceled is not called when promise is deleted

QFuture<int> getInteger()
{
    auto promise = QSharedPointer<QPromise<int>>::create();
    QTimer::singleShot(1000, qApp, [promise] () mutable {
        promise->start();
        QTimer::singleShot(1000, qApp, [] () { qApp->quit(); });
    });
    return promise->future();
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    auto future = getInteger();

    future
        .onCanceled([]{
            qDebug() << "Canceled";
            return  -1;
        });

    QFutureWatcher<int> watcher;
    watcher.setFuture(future);

    QObject::connect(&watcher, &QFutureWatcher<int>::canceled, []{ qDebug() << "watcher canceled"; });
    QObject::connect(&watcher, &QFutureWatcher<int>::finished, []{ qDebug() << "watcher finished"; });
    QObject::connect(&watcher, &QFutureWatcher<int>::started, []{ qDebug() << "watcher started"; });

    return a.exec();
}

Canceled
watcher started
watcher canceled
watcher finished

watcher started
watcher canceled
watcher finished