Henkan_Mod (<henkan>) undefined in Emacs (AltGr elsewhere in X)

[Bastien]

Dear all,

I have a thinkpad X61 with a Japanese keyboard.  

I use this in .xmodmaprc to set the Henkan key to AltGr:

  add mod5 = Henkan_Mode

This works in terminal and other X applications, but it 
doesn't work in GNU Emacs: pressing the Henkan key says
"<henkan> is undefined".

Any hint on how to fix this (very annoying) problem?

As a workaround, can I use global-set-key to remap the
<henkan> key to the AltGr key?

Thanks a lot in advance,

I'm using latest ArchLinux and GNU Emacs 24.0.50.2 
(i686-pc-linux-gnu, GTK+ Version 2.22.1) of 2011-03-16.

-- 
 Bastien