My AIX 5.3 update userPassword in clear on LDAP

I'm running OpenLDAP 2.3.43 in a linux Host.
I have a AIX 5.3 TL9 as client.

All works fine with client authentification, information reading in LDAP server and all the stuff.

The only problem is :

when I run passwd with an LDAP user it updates password (userPassword) with clear text.

Somebody allready had this problem ?

Thanks for your help