[Vala] Is creating dbus interfaces in type modules (plugins) broken?

[PCMan <pcman tw gmail com>]

Hello,
I tried to develop some type modules for my program.
Everything works fine initially and [ModuleInit] registered GObject dynamic
classes automagically as expected.
However, after I move a previously working dbus interface to that type
module, I got crashes.

My source code is here:
http://lxde.git.sourceforge.net/git/gitweb.cgi?p=lxde/lxpanel2;a=summary

A google search lead me to a similar report from others:
https://mail.gnome.org/archives/vala-list/2012-September/msg00125.html

Is this a known bug? Or is there anyway to overcome this?
I like vala a lot and I don't want to rewrite the whole program in C again
just because some little problems.

Thanks in advance.