Problem is noted here: https://issues.apache.org/jira/browse/SPARK-5949
I tried this as a workaround: import org.apache.spark.scheduler._ import org.roaringbitmap._ ... kryo.register(classOf[org.roaringbitmap.RoaringBitmap]) kryo.register(classOf[org.roaringbitmap.RoaringArray]) kryo.register(classOf[org.roaringbitmap.ArrayContainer]) kryo.register(classOf[org.apache.spark.scheduler.HighlyCompressedMapStatus]) kryo.register(classOf[org.roaringbitmap.RoaringArray$Element]) kryo.register(classOf[org.roaringbitmap.RoaringArray$Element[]]) kryo.register(classOf[short[]]) in build file: libraryDependencies += "org.roaringbitmap" % "RoaringBitmap" % "0.4.8" This fails to compile: ...:53: identifier expected but ']' found. [error] kryo.register(classOf[org.roaringbitmap.RoaringArray$Element[]]) also: :54: identifier expected but ']' found. [error] kryo.register(classOf[short[]]) also: :51: class HighlyCompressedMapStatus in package scheduler cannot be accessed in package org.apache.spark.scheduler [error] kryo.register(classOf[org.apache.spark.scheduler.HighlyCompressedMapStatus]) Suggestions? Arun