this test fails: public class XStreamTest extends TestCase { public static class MyMap extends HashMap implements Map { } public void testCanExportSubclassesOfMap() { MyMap myMap = new MyMap(); myMap.put("hehe", "hoho"); XStream xstream = new XStream(); String xml = xstream.toXML(myMap); MyMap myOtherMap = (MyMap) xstream.fromXML(xml); assertEquals(myMap, myOtherMap); } }