AE in Bounds when running word count

ERROR 20:01:24,693 Exception in thread Thread[Thrift:16,5,main]
java.lang.AssertionError: [DecoratedKey(663380155395974698, 6b6579333137),max(-8100212023555812159)]
        at org.apache.cassandra.dht.Bounds.<init>(Bounds.java:41)
        at org.apache.cassandra.dht.Bounds.<init>(Bounds.java:34)
        at org.apache.cassandra.thrift.CassandraServer.get_paged_slice(CassandraServer.java:1041)
        at org.apache.cassandra.thrift.Cassandra$Processor$get_paged_slice.getResult(Cassandra.java:3478)
        at org.apache.cassandra.thrift.Cassandra$Processor$get_paged_slice.getResult(Cassandra.java:3466)
        at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:32)
        at org.apache.thrift.TBaseProcessor.process(TBaseProcessor.java:34)
        at org.apache.cassandra.thrift.CustomTThreadPoolServer$WorkerProcess.run(CustomTThreadPoolServer.java:199)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:662)