XML Escaping variable names with JettisonMappedXmlDriver

When I serialize a simple User (first_name, lastName) object into JSON,
for some reason when I use JettisonMappedXmlDriver it converts single
underscores '' into double underscores '_'. When I use the
JsonHierarchicalStreamDriver I do not have this problem, however I need
to be able to de-serialize so I must use the Jettison driver.