Ok, I think I got it.
I was using a 'SUP inetOrgPerson STRUCTURAL' to my new scheme.
So, when I've changed to 'SUP top AUXILIARY' I finally could add my new attributes.
I think it's because ldapmodify was trying to modify the structural object to my entry and it's impossible (just at creation time).
So, here's my ldif (it's working):
dn: uid=unicorn,ou=ground,dc=dinosaurs,dc=jurassic,dc=history changetype: modify add: objectClass objectClass: oilCorporation - add: oilCorporationTypeOfThing oilCorporationTypeOfThing: withcandle
[]'s Alexander Brazil - Rio de Janeiro
---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.