samba - Apr 2009 - [samba4][LDAP]: memberOf: attribute type undefined

Dear

i'm trying to run samba4 on a debian lenny with LDAP backend

when execute 
slapd -f /etc/samba/ldap/slapd.conf -h ldapi://%2Fetc%2Fsamba%2Fldap%
2Fldapi -d4294967295

the slapd server crash with this output : 

<<< dnPrettyNormal: <cn=samba-admin,cn=samba>,
<cn=samba-admin,cn=samba>
line 57 (refint_attributes  nonSecurityMemberBL nonSecurityMember
msDS-NonMembersBL msDS-NonMembers directReports manager
bridgeheadServerListBL bridgeheadTransportList msDS-ObjectReferenceBL
msDS-ObjectReference msCOM-UserLink msCOM-UserPartitionSetLink
msDs-masteredBy msDS-hasMasterNCs siteObjectBL siteObject queryPolicyBL
queryPolicyObject masteredBy hasMasterNCs managedObjects managedBy
serverReferenceBL serverReference memberOf member)
/etc/samba/ldap/slapd.conf: line 57: refint_attributes <memberOf>:
attribute type undefined
lt-slapd destroy: freeing system resources.
slapd stopped.

Howto fix it ?

best regards.