QNetworkReply readAll response is empty when there is an error code

Response of QNetworkReply::readAll is empty when QNetworkReply::error() != NoError. Is this normal?

I've a Node+Express server that always send a detailed description in case of http status different of 200; I cant get this description from my Qt client base on QNAM. Qt version is 5.3, OS Win 7 64b.

This is my code, really I don't think this can help.

PendingRequest *Foo::sendMsg(QStandardItem *requestItem, HTTP_METHOD_ID method, QString path)
{
    PendingRequest *pReq = new PendingRequest(method);

    QString url = QString("https://%1:%2%3").arg(host, QString::number(port), path);
    QNetworkRequest qNetReq = QNetworkRequest(QUrl(url));

    //set headears
    qNetReq.setHeader(QNetworkRequest::KnownHeaders::UserAgentHeader, HttpUserAgent);
    qNetReq.setRawHeader("Connection", "Keep-Alive");
    if(!credentials.isEmpty())
    {
        qNetReq.setRawHeader("Authorization", QByteArray("Basic ")+credentials);
    }
    if(!sessionId.isEmpty())
    {
        qNetReq.setRawHeader("Session-Id", sessionId);
    }

    //send request
    QNetworkReply *reply;
    if(method == HTTP_METHOD_ID::POST)
    {
        qNetReq.setHeader(QNetworkRequest::KnownHeaders::ContentTypeHeader, "application/json");
        QByteArray data = outHandlerList[outHandlerIndex](requestItem);
        reply = netManager.post(qNetReq, data);
    }
    else
    {
        reply = netManager.get(qNetReq);
    }

    connect(reply, SIGNAL(finished()), this, SLOT(handleResponse()));
    connect(reply, SIGNAL(sslErrors(QList<QSslError>)), this, SLOT(handleSslErrors(QList<QSslError>)));

    return pReq;
}

and this where I handle response:

void Foo::handleResponse()
{
    QNetworkReply *reply = qobject_cast<QNetworkReply *>(sender());

    if(reply->hasRawHeader("Session-Id"))
        sessionId = reply->rawHeader("Session-Id");

    PendingRequest *pReq = pendingRequestMap.contains(reply) ? pendingRequestMap.take(reply) : 0;
    Q_ASSERT(pReq);

    QStandardItem *responseItem = 0;
    QString error;

    if(reply->error() != QNetworkReply::NoError)
    {
        qDebug() << "readAll: ", reply->readAll(), "error: ", reply->errorString();
        error = reply->errorString();
    }
    else
    {
        responseItem = inHandlerList[pReq->inHandlerIndex](reply, error, pReq);
    }

    reply->deleteLater();
}

Thanks a lot for your help.