Comment on email thread: Digging a little bit more into my code, I noticed (casually) that setting my custom marshallers one before the other, the error disappear and everything works fine. It seems like I have to register my marshallers in the same order they are specified into the property “MessageMarshallers" of the "resource-adapter/connection-defitions/connection-definition” definition in standalone.xml. I don’t think this is the expected behaviour!