I agree both scanarios should be addressed. Addressing the interface issue is not hard as we can do type.isInterface() However this leaves two problems. Both are not common. use cases. 1. Abstract classes which if someone uses it is imposible to get it to work, since it will fail on 'Field.set'. 2. Another problem is when a user uses his own sub interface. I think the code should address the first two issues and state in the documentation not to use abstract classes or sub interfaces of Collection, Set, List and Map for field mapping. (Maybe add an clear exception message) View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4159483#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...