Custom GObject properties seem to be broken with python

Hi!
I’m having troubles with the gnome nightly runtime and GObject properties. When I define a new property with something like this GObject.Property(type=int, default=-1) I’ll get errors like this:

TypeError: Method do_get_property() on class Gtk.Box is ambiguous with methods in base classes GObject.InitiallyUnowned and GObject.Object

Last week the same code ran just fine and with the stable runtime (v47) it still does. Has someone an idea what I’m doing wrong here?

Please, file a bug against pygobject.

Here is the issue.

Apparently it’s not just a pygobject bug.