List<Integer> RuntimeError: Unknown OpCode in the stream: 0x0 (at offset 0x8C)

[skotep]

In Java I create an ArrayList of two Integers, e.g.,

List<Integer> data = new ArrayList<>();
data.add(1)
data.add(2)

which serializes to

b'\xac\xed\x00\x05sr\x00\x13java.util.ArrayListx\x81\xd2\x1d\x99\xc7a\x9d\x03\x00\x01I\x00\x04sizexp\x00\x00\x00\x02w\x04\x00\x00\x00\x02sr\x00\x11java.lang.Integer\x12\xe2\xa0\xa4\xf7\x81\x878\x02\x00\x01I\x00\x05valuexr\x00\x10java.lang.Number\x86\xac\x95\x1d\x0b\x94\xe0\x8b\x02\x00\x00xp\x00\x00\x00\x01sq\x00~\x00\x02\x00\x00\x00\x02x'

javaobj.loads(bytes)

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "javaobj.py", line 190, in loads
    ignore_remaining_data=ignore_remaining_data)
  File "javaobj.py", line 171, in load
    return marshaller.readObject(ignore_remaining_data=ignore_remaining_data)
  File "javaobj.py", line 501, in readObject
    _, res = self._read_and_exec_opcode(ident=0)
  File "javaobj.py", line 568, in _read_and_exec_opcode
    return opid, handler(ident=ident)
  File "javaobj.py", line 833, in do_object
    opcode, obj = self._read_and_exec_opcode(ident=ident + 1)
  File "javaobj.py", line 564, in _read_and_exec_opcode
    .format(opid, position))
RuntimeError: Unknown OpCode in the stream: 0x0 (at offset 0x8C)

If I only have one integer in the list then it loads fine. I have the problem with Doubles as well as Integers. Strings seem to work fine though.