Spring Cloud Stream - Concurrency

Can you show your configuration? I just tested it and it worked exactly as expected...

spring.cloud.stream.bindings.input.group=foo
spring.cloud.stream.bindings.input.consumer.concurrency=10

with

@SpringBootApplication
@EnableBinding(Sink.class)
public class So48953227Application {

    public static void main(String[] args) {
        SpringApplication.run(So48953227Application.class, args);
    }

    @StreamListener(Sink.INPUT)
    public void listen(String in) {

    }

}

and

immediately, without sending any messages