QDBusServiceWatcher does not watch for the services appearing on a bus

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QDBusServiceWatcher serviceWatcher(
                "org.freedesktop.GeoClue2",
                QDBusConnection::systemBus(),
                QDBusServiceWatcher::WatchForRegistration
                | QDBusServiceWatcher::WatchForUnregistration
                | QDBusServiceWatcher::WatchForOwnerChange);

    QObject::connect(&serviceWatcher, &QDBusServiceWatcher::serviceRegistered,
                     [](const QString &service) {
        qDebug() << "Registered:" << service;
    });
    QObject::connect(&serviceWatcher, &QDBusServiceWatcher::serviceUnregistered,
                     [](const QString &service) {
        qDebug() << "Unregistered:" << service;
    });
    QObject::connect(&serviceWatcher, &QDBusServiceWatcher::serviceOwnerChanged,
                     [](const QString &service, const QString &oldOwner, const QString &newOwner) {
        qDebug() << "Owner changed:" << service << oldOwner << newOwner;
    });

    return a.exec();
}

#include <gio/gio.h>

static void
on_name_appeared(GDBusConnection *connection,
                  const gchar *name,
                  const gchar *name_owner,
                  gpointer user_data)
{
    g_print ("Name %s on the system bus is owned by %s\n",
             name,
             name_owner);
}

static void
on_name_vanished(GDBusConnection *connection,
                  const gchar *name,
                  gpointer user_data)
{
    g_print ("Name %s does not exist on the system bus\n",
             name);
}

int
main(int argc, char *argv[])
{
    const guint watcher_id = g_bus_watch_name(
        G_BUS_TYPE_SYSTEM,
        "org.freedesktop.GeoClue2",
        G_BUS_NAME_WATCHER_FLAGS_AUTO_START,
        on_name_appeared,
        on_name_vanished,
        NULL, NULL);

    GMainLoop *loop = g_main_loop_new(NULL, FALSE);
    g_main_loop_run(loop);

    g_bus_unwatch_name(watcher_id);

    return 0;
}