Index: src/main/java/org/apache/hadoop/hbase/io/HbaseObjectWritable.java =================================================================== --- src/main/java/org/apache/hadoop/hbase/io/HbaseObjectWritable.java (revision 1340108) +++ src/main/java/org/apache/hadoop/hbase/io/HbaseObjectWritable.java (working copy) @@ -477,8 +477,9 @@ int length = list.size(); out.writeInt(length); for (int i = 0; i < length; i++) { - writeObject(out, list.get(i), - list.get(i).getClass(), conf); + Object elem = list.get(i); + writeObject(out, elem, + elem == null ? Writable.class : elem.getClass(), conf); } } else if (declClass == String.class) { // String Text.writeString(out, (String)instanceObj);