def add_utf8_header(self, start_response):
        def start_response_wrapper(status, headers):
            headers_dict = dict(headers)
            if headers_dict['Content-Type'] == 'text/html':
                headers_dict['Content-Type'] = 'text/html; charset=UTF-8'
            return start_response(status, headers_dict.items())
        return start_response_wrapper