NullPointerException in Kafka-Spout

KafkaSpout reports following error:
java.lang.NullPointerException
at java.util.TreeMap.rotateLeft(TreeMap.java:2220) ~[?:1.8.0_77]
at java.util.TreeMap.fixAfterInsertion(TreeMap.java:2287) ~[?:1.8.0_77]
at java.util.TreeMap.put(TreeMap.java:582) ~[?:1.8.0_77]
at org.apache.storm.kafka.PartitionManager.fill(PartitionManager.java:235) ~[stormjar.jar:?]
at org.apache.storm.kafka.PartitionManager.next(PartitionManager.java:138) ~[stormjar.jar:?]
at org.apache.storm.kafka.KafkaSpout.nextTuple(KafkaSpout.java:135) ~[stormjar.jar:?]
at applications.spout.KafkaSpoutWrapper.nextTuple(KafkaSpoutWrapper.java:64) ~[stormjar.jar:?]
at org.apache.storm.daemon.executor$fn_7885$fn7900$fn_7931.invoke(executor.clj:645) ~[storm-core-1.0.1.jar:1.0.1]
at org.apache.storm.util$async_loop$fn__625.invoke(util.clj:484) [storm-core-1.0.1.jar:1.0.1]
at clojure.lang.AFn.run(AFn.java:22) [clojure-1.7.0.jar:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_77]