[Serusers] nathelper & force_rtp_proxy(); problem

[Mathieu MALAISE]

Hi all,

Starting with the "rtpproxy install notes", I try to install SER + 
nathelper + rtpproxy.
I took the config file from klaus 
(http://lists.iptel.org/pipermail/serusers/2003-July/001834.html)
with the modification from Maxim ( if (status=~"2[0-9][0-9]") -> if 
(status=~"[12][0-9][0-9]") ).
and when I launch ser (/etc/init.d/ser start), I got this debug message 
(I put the debug to level 7, no fork):

Starting ser:  0(10136) loading module /usr/lib/ser/modules/nathelper.so
 0(10136) loading module /usr/lib/ser/modules/textops.so
 0(10136) loading module /usr/lib/ser/modules/sl.so
 0(10136) loading module /usr/lib/ser/modules/tm.so
 0(10136) loading module /usr/lib/ser/modules/rr.so
 0(10136) loading module /usr/lib/ser/modules/maxfwd.so
 0(10136) loading module /usr/lib/ser/modules/usrloc.so
 0(10136) loading module /usr/lib/ser/modules/registrar.so
 0(10136) set_mod_param_regex: usrloc matches module usrloc
...
 0(10136) find_export: found <sl_reply_error> in module sl_module 
[/usr/lib/ser/modules/sl.so]
 0(10136) find_export: <force_rtp_proxy> not found
 0(10136) find_export: <force_rtp_proxy> not found
 0(10136) parse error (145,33-34): unknown command, missing loadmodule?

ERROR: bad config file (2 errors)
 0(10136) DEBUG: tm_shutdown : start
...

Why is force_rtp_proxy not found ? It's part of the nathelper module, 
isn't it ?

Thank you all for your help !
Mathieu.