Custom timeout with Message.RECEIVE_TIMEOUT not working with hc5 / hc

Hi, I am trying to set custom read timeouts for WS operations in an interceptor:

public class CustomReadTimeoutInterceptor extends AbstractPhaseInterceptor<Message> {
...
@Override
public void handleMessage(Message message) {
  message.put(Message.RECEIVE_TIMEOUT, timeoutMillis);
}
...

That works well when using the JDK http client, but it does NOT work with the hc5 async client.
It looks like requests issued in parallel affect each others timeout settings.

Download the attached sample project, which contains a CustomReadTimeoutInterceptor and starts two requests in parallel with different timeouts (4 and 2 seconds).

Execute both 

mvn

and

mvn -DuseAsync

and compare the output. The output of the first will be like

CLIENT[19]: Duration: 2010 millis 
CLIENT[29]: Duration: 4211 millis

(which is as expected) whereas the second - using hc5 async - will result in

CLIENT[29]: Duration: 4269 millis  
CLIENT[19]: Duration: 4012 millis

Now I am wondering if my code is somehow incorrect or if it is cxf's fault...