First connect to the signal, then register the object, and only at last register the service.
Otherwise it might expose a not yet fully operational service on DBus.

I made an app that listens for Unity service to be registered and send its badge info once it's there. Without this it would fire the signal before we connected to it resulting in the badge not showing on Plasma startup, with this patch it works.
iirc this is also what Thiago always said you should do when he did the threaded dbus changes in Qt 5.6