On OS/400, with jdk15, when I deploy JBoss Seam, I get a ClassFormatError (see bellow). When I replace javassist by cglib, it works again. When I use JBoss Seam on my PC, everything works fine. When I create a small application (no Seam) with only Hibernate, I get the exact same exception. Any idea of how to solve the issue? (I do not want to replace javassist by cglib) Caused by: javassist.CannotCompileException: by java.lang.ClassFormatError: org/javassist/tmp/java/lang/Object_$$_javassist_1 0000 6305 at java.lang.Throwable.(Throwable.java:196) at java.lang.Exception.(Exception.java:41) at javassist.CannotCompileException.(CannotCompileException.java:73) at javassist.util.proxy.FactoryHelper.toClass(FactoryHelper.java:165) at org.jboss.seam.util.ProxyFactory.createClass(ProxyFactory.java:186) ... 87 more Caused by: java.lang.ClassFormatError: org/javassist/tmp/java/lang/Object_$$_javassist_1 0000 6305 at java.lang.Throwable.(Throwable.java:196) at java.lang.Error.(Error.java:49) at java.lang.LinkageError.(LinkageError.java:36) at java.lang.ClassFormatError.(ClassFormatError.java:35) at java.lang.ClassLoader.defineClass(ClassLoader.java:651) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at javassist.util.proxy.FactoryHelper.toClass2(FactoryHelper.java:177) at javassist.util.proxy.FactoryHelper.toClass(FactoryHelper.java:159) ... 88 more View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4111332#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...