HTTP/2: connection to http:// host (that does not support http2) is always failing

#include <QtNetwork/QtNetwork>
int main(int argv, char **argc) {
    QCoreApplication app(argv, argc);
    QNetworkAccessManager qnam;
    QObject::connect(&qnam, &QNetworkAccessManager::finished, [&app](QNetworkReply* rep) {
        qDebug() << "RESULT:" << rep->error();
        app.quit();
    });
    QNetworkRequest req(QUrl("http://woboq.com")); // any http url would do
    req.setAttribute(QNetworkRequest::HTTP2AllowedAttribute, true);
    qnam.get(req);
    return app.exec();
}

/*
 prints:

qt.network.http2: connection error: invalid frame size
qt.network.http2: stream 1 finished with error: "invalid frame size"
RESULT: QNetworkReply::NetworkError(ProtocolFailure)
*/