Github user yanghua commented on the issue: https://github.com/apache/flink/pull/6231 @zentol we really caused this exception, in our inner Flink version, we customized flink-table and implemented stream and dim table join. I think the default constructor is needed by deserialization. Whatever it takes, the author who wrote this code misunderstood the variable `nestedSerializers ` could be null(in current case), but it did not happens. The truth is : the elements in `nestedSerializers` could be null. We add a judgement and fixed this NPE, now it works OK.