YES, it is a classical classloader problem. I was putting the class mypgk.ImportManager not only in the ejb.jar, but also in mywar.war/WEB-INF/lib. After removing the class from WEB-INF/lib, no ClassCastException anymore. I am fully aware of the type-incompatibility when loaded from different class-loaders. But I don't understand one thing. JBoss is based on a hierarchical class-loader, right? classes in app.ear are also available in deployment-units inside of the EAR, but not in "sibling-deployment-units". The scenario: mypkg.ImportManager.class is available in ejb-package.jar ONLY. How can this class be loaded in webapp.war deployment-unit without being deployed ?? I'd expect a ClassNotFoundException ! View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4093965#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...