Search by customized attribute in OpenLdap

Hi, I've installed OpenLdap, and defiened the following schema:

attributetype ( 1.2.840.113556.1.4.221 NAME 'sAMAccountName' SYNTAX '1.3.6.1.4.1.1466.115.121.1.15' SINGLE-VALUE ) objectclass ( 1.2.840.113556.1.5.6 NAME 'securityPrincipal' SUP top AUXILIARY MUST (sAMAccountName ) MAY (mail))

I've created an entry as follows:

dn: cn=John Smith,ou=External Users,dc=xxx,dc=yyy,dc=com cn: John Smith objectClass: person objectClass: securityPrincipal mail: test@test.com sn: Smith userPassword: myPassword sAMAccountName: smith

Then I try to get the entry looking for (sAMAccountName='smith'), but it doesn't work. If I look for (cn='John Smith') it founds the entry. So what do I need to do in order to be able to search by sAMAccountName?

Thanks

Jose