FeignClient fallback 错误

@FeignClient(name = "hello", fallback = HystrixClientFallback.class)
    public interface HystrixClient {
        @RequestMapping(method = RequestMethod.GET, value = "/hello")
        Hello iFailSometimes();
    }
    
    public class HystrixClientFallback implements HystrixClient {
        @Override
        public Hello iFailSometimes() {
            return new Hello("fallback");
        }
    }
    
    @Configuration
    public class FooConfiguration {
        @Bean
        @Scope("prototype")
        public Feign.Builder feignBuilder() {
            return Feign.builder();
        }
        
        @Bean
        public HystrixClientFallback fb(){
            return new HystrixClientFallback();
        }
……
    }