Delivery count decrement twice if message sends to deadletter address

There is a queue with max-delivery-attempts = 1. There is core bridge (or my custom consumer) which increment delivery count and cancel each message using this method. If I put 3 messages to the queue, all they will be moved to deadletter address after attempt to deliver. After that сall queue.getInstantMessageCount() will return "-3". This happens because decDelivering method called twice: first in cancel(MessageReference, long), second in postAcknowledge(MessageReference).

Test case:
//my consumer example
public class MyConsumer implements Consumer {
public HandleStatus handle(final MessageReference messageReference) throws Exception { 
messageReference.handled();
messageReference.incrementDeliveryCount();
executor.submit(new Runnable() {
public void run() {
queue.cancel(messageReference,System.currentTimeMillis());
System.out.println(queue.getInstantMessageCount());
}
});
return HandleStatus.HANDLED;
}
}

Executor executor; //Some executor

System.out.println(queue.getInstantMessageCount()); //print 0;

queue.addConsumer(new MyConsumer);
queue.deliverAsync();

//putting message to Queue
//will print -1