QDBusConnection::connect() doesn't support filtering on arguments

I'd like to connect to a DBus signal. I can do this using QDBusConnection::connect(), which internally calls dbus_bus_add_match(). But I want to react only on signals where the first argument matches a specific string.

According to this posting:
http://osdir.com/ml/freedesktop.dbus/2005-08/msg00122.html
this is possible using dbus_bus_add_match().

I'd like to be able to use the dbus functionality of filtering signals also on their argument values also from within Qt applications. Maybe an extended connect() ? Or a special function addFilters() ?