How to migrate LDAP server?

My GitLab installlation uses LDAP authentication. I have a new LDAP server in wich I created the same existing user from old LDAP server so people can login with the same username and having all the same contributions, configurations etc in GitLab as before. Just changing the LDAP configuration resulted in the user my.user to be logged in as a blank new user called my.user1.
The username and the email attributes are mapped in GitLab config to the same values in both LDAP servers.
Is there a way to make GitLab see this login from a new LDAP server as the old one? Or the solution is something like migrating my.user1 to my.user?