[Mac 10.8] QSystemTrayIcon::showMessage() shows nothing in notification center

Since Qt 5.1, QSystemTrayIcon::showMessage() uses Growl on mac os prior to 10.8 and uses the native notification center on 10.8+.
I'm on 10.8.4, and a simple call to showMessage() shows nothing on my mac, is correctly working on my VM (Win XP) and is correctly working on Mac OS 10.9 (tested with a compiled (on 10.8.4) app)

// ... ///
QSystemTrayIcon    *sysTray(QIcon(":/icons/svg"));

sysTray->show();
sysTray->showMessage(QObject::tr("First start"), QObject::tr("Generating UUID..."));
// ... //