Concurrent modification exception during connection cleanup in buffer server

ERROR com.datatorrent.bufferserver.server.Server: Buffer server Server@56cfec7c\{address=/0:0:0:0:0:0:0:0:45081} failed to tear down subscriber Subscriber@2ff22212{ln=LogicalNode@36d87f9eidentifier=tcp://xxxxxx:45081/2.output.1, upstream=2.output.1, group=rand_console/3.input, partitions=[], iterator=com.datatorrent.bufferserver.internal.DataList$DataListIterator@6caeed6a{da=com.datatorrent.bufferserver.internal.DataList$Block@506501e4{identifier=2.output.1, data=16777216, readingOffset=0, writingOffset=1822, starting_window=59dc9c3000000001, ending_window=59dc9c3000000055, refCount=2, uniqueIdentifier=0, next=null, future=null}}}}.java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(HashMap.java:922)
	at java.util.HashMap$KeyIterator.next(HashMap.java:956)
	at com.datatorrent.bufferserver.internal.LogicalNode.removeChannel(LogicalNode.java:118)
	at com.datatorrent.bufferserver.server.Server$3.run(Server.java:410)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
	at java.util.concurrent.FutureTask.run(FutureTask.java:262)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:745)