olcAccess don't working

Dears,

I've configured a META ldap instance pointing to a LDAP backend. In this backend, there are a few ACLs but which ones don't restrict ldapsearch that I do from the META frontend. I just have an issue when I set some ACLs on the META frontend and more specially when I insert attrs=xxx in the ACL.

Here is my ACL = OK

olcAccess : {0}to dn.one="ou=staff,o=mobistar.be" by dn="uid=a0621004,ou=ObeExternalITOnGcp,ou=partners,o=mobistar.be" read

NOT OK olcAccess : {0}to dn.one="ou=staff,o=mobistar.be" attrs=uid by dn="uid=a0621004,ou=ObeExternalITOnGcp,ou=partners,o=mobistar.be" read

Can you explain why when I restrict to an attribute, my ldapsearch didn't provide me any response as expected ?

Thx in advance, J-L.