Error on length validation if it's with server validation

[fabio-ravizzotti]

Hi,
there is a possible problem when you work with (in my case) length and server validation.

I'have an input field for "username" that I need to validate both lenght and server.
Lenght for maximum number of charter.
Server for avoid duplicated usernames.

This is the html code:
<input type="text" class="form-control" data-validation-help="ATTENZIONE: l'username servir&agrave; per l'accesso al sito." required data-validation="length server" data-validation-length="max56" data-validation-url="/mysite/index.php/setting/check_username" id="ut_username" name="ut_username" required />

The function "check_username" returns the follows jsons:
-if it's TRUE: {"valid":true,"message":""}
-if it's FALSE: {"valid":false,"message":"Username already exists"}

The issue is: if you first insert a duplicated username, it appears the right message, but if after you insert a username longer than 56 character it prints always the message for the duplicated username and not the right message.

May you check it, please?