# Ice::UnknownUserException

## Overview

### local exception UnknownUserException extends UnknownException

An operation raised an incorrect user exception. This exception is raised if an operation raises a user exception that is not declared in the exception's `throws` clause. Such undeclared exceptions are not transmitted from the server to the client by the Ice protocol, but instead the client just gets an UnknownUserException. This is necessary in order to not violate the contract established by an operation's signature: Only local exceptions and user exceptions declared in the `throws` clause can be raised.