openldap and kerberos auth-to-local rules

Hello list.

I successfuly configured OpenLDAP for kerberos autentication, and user 
mapping:
authz-regexp "uid=([^,]+),cn=gssapi,cn=auth"
     "ldap:///ou=users,dc=futurs,dc=inria,dc=fr??sub?(uid=$1)"

However, mapping doesn't work when autenticating with a user from a 
different realm than the one from the server. The logs show the realm is 
not stripped from username, as it should be:
Oct  5 17:30:45 babaorum slapd[28598]: conn=24 op=2 BIND 
authcid="[email protected]" authzid="[email protected]"
Oct  5 17:30:45 babaorum slapd[28598]: conn=24 op=2 BIND 
dn="[email protected],cn=gssapi,cn=auth" mech=GSSAPI 
sasl_ssf=56 ssf=56

authcid should be 'rousse', not '[email protected]'. This is a 
classic problem, and kerberos provides mapping rules for users of 
external domains, such as described here:
http://www.fnal.gov/docs/strongauth2003/html/krb5conf.html

I used those rules succesfully with mod_krb, for instance. However, 
openldap seems to ignore them. I had to change the previous regexp to:
authz-regexp "uid=([^,@]+)(@[^,]+)?,cn=gssapi,cn=auth"
     "ldap:///ou=users,dc=futurs,dc=inria,dc=fr??sub?(uid=$1)

Is this intentional ?
-- 
BOFH excuse #58:

high pressure system failure