Network proxy cache is broken

The attached example demonstrates the problem. It has been reproduced using Windows and Linux.

When using the following piece of code where username/password is set in the proxy object, everything works fine:

QNetworkProxy::setApplicationProxy(QNetworkProxy(QNetworkProxy::HttpProxy, "someHostName",somePort, "someUserName", "somePassword"));

However, if the code is changed to:

QNetworkProxy::setApplicationProxy(QNetworkProxy(QNetworkProxy::HttpProxy, "someHostName", somePort));

without passing username/password, and a dialog is popped up to get the username and password and pass it to the QAuthenticator as shown below then it does not work:

void HttpWindow::slotProxyAuthenticationRequired(const QNetworkProxy& proxy, QAuthenticator* authenticator) {
QDialog dlg;
Ui::Dialog ui;
ui.setupUi(&dlg);
dlg.adjustSize();
ui.siteDescription->setText(tr("%1 at %2").arg(authenticator->realm()).arg(url.host()));

if (dlg.exec() == QDialog::Accepted) {
authenticator->setUser(ui.userEdit->text());
authenticator->setPassword(ui.passwordEdit->text());
}
}

These lines are shown in the output:

QNetworkAccessCache::addEntry: overriding active cache entry 'auth:proxy-http://...
QNetworkAccessCache::addEntry: overriding active cache entry 'auth:proxy-http://...
QNetworkAccessCache::addEntry: overriding active cache entry 'auth:proxy-http://...'

It can be fixed as follows:

void HttpWindow::slotProxyAuthenticationRequired(const QNetworkProxy& proxy, QAuthenticator* authenticator) {
QDialog dlg;
Ui::Dialog ui;
ui.setupUi(&dlg);
dlg.adjustSize();
ui.siteDescription->setText(tr("%1 at %2").arg(authenticator->realm()).arg(url.host()));

if (dlg.exec() == QDialog::Accepted) {
authenticator->setUser(ui.userEdit->text());
authenticator->setPassword(ui.passwordEdit->text());
QNetworkProxy p(proxy);
p.setUser(ui.userEdit->text());
p.setPassword(ui.passwordEdit->text());
QNetworkProxy::setApplicationProxy(p);
}

}

but that's a dirty hack ...