LDAP avoid special caracter

We setup Jasper CE 6.4.2 to use our Acrive Directory Microsoft LDAP.

In our AD no user name use special caracter.

Jasper permit connection also to user writed with accent, for example

User "ale" can login with "ale" name but also with name "àle".

After login Jasper create a new user with name àle.

Any idea on how to avoid this issue?

Thanks