The point is that you are trying to achieve something with a framework that you used to do with a language extension. Given AspectJ is a language extension of Java, its compiler would know to recognize that Initiateur now implements InitiateurI. JBoss AOP is not an extension of Java, it is a framework. Hence you have to use javac standard compiler to compile your code; javac won't recognize that after compiling you are going to use a tool that makes Initiateur implemnt InitiateurI. So, you have to use a casting: | ... | if (i==1){memento1= Initiateur1Memento.createMementoFor((InitiateurI) initiateur);} | ... | Initiateur1Memento.setMemento((InitiateurI) initiateur, memento1); | ... | View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4258401#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...