Trying to create a username having more then 592 characters give error message

Steps to Reproduce:
1. Launch JIRA 3.13.1
2. Login as admin user.
3. Go to User browers and click "Add user"
4. In the username field copy a string having 593 characters

Result:
1. It give error message "com.opensymphony.user.ImmutableException:"
2. Detail log file is attached.

Expected:
1. user should be allowed to create user. If the characters are more then the desired limit, a proper error message should be displayed.