I am using JDK 1.6.0_02. I am referring to javax.xml.stream.XMLInputFactory.newInstance(String, ClassLoader) method. This method does not treat "null classloader" correctly. If I want to use the classloader that loads XMLInputFactory.class, then in JDK 1.6 env, it is obviously null since the bootstrap classloader has this class. In such a situation, the implementation in JDK 1.6 falls back to Thread's context class loader, which I think is against the behavior defined in the spec. It should use the three argument variant of Class.forName with null as the last argument.