ldap_bind: Invalid credentials (49)

Hi, I try to add the samba.schema in my openldap server (Debian Wheezy), default installed. slapd: 2.4.31 ldap-utils 2.4.31

I followed this tutorial https://help.ubuntu.com/10.04/serverguide/samba-ldap.html

I can use ldapsearch, ldapadd and ldapmodify with my cn=admin,dc=example,dc=com password but when I try to add the new schema to the directory with

ldapadd -x -D cn=admin,cn=config -W -f /tmp/cn=samba.ldif

I get ldap_bind: Invalid credentials (49)

Is there a different password for cn=admin,cn=config? I was never asked to create it. And how can I change it if necessary?

Many thanks!!!