Gtk: Multi_key ceases to work

[Kai Großjohann]

With many applications (including Emacs using the default toolkit),
it worked to assign the Multi_key keysym to some keycode.  Then I
could type Multi_key followed by " followed by a, say, to generate
ä.  And Multi_key followed by s and then s again generated ß.

But now I've compiled Emacs with Gtk (it's really great, btw!) and
this ceases to work.  Emacs beeps (or flashes, because of
visible-bell) when I hit the Multi_key.

What do I do now?  Is this a bug in the Gtk port or a bug in Kai?
-- 
Ambibibentists unite!