wp_insert_term breaking descriptions

Hello everybody;

I have a custom script with this:

$valor['description'] = "Eso no es un árbol";

wp_insert_term(
            $valor['term'], // the term
            'directorio', // the taxonomy
            array(
                'description'=> $valor['description']

            )
        );

And I just got inserted: Eso no es un

It looks like I have to do something to keep the spanish chars but I tried mysql_escape_string and other functions and nothing seem to work.

Do you have any suggestions?