I have the following code in my webapp:

try {
 Naming.rebind ( "//localhost:1099/myAppName", myClass );
}
catch ( Exception e ) { e.printStackTrace(); }

and it works fine in JBoss 4.2.3.
Now I install JBoss 5.1.0 and deploy the same mywebapp.war in it.
And get the following exception:

 (ajp-localhost%2F127.0.0.1-8009-7) java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
 java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
 java.lang.ClassNotFoundException: my.domain.webapp.MyClass_Stub
(ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:396)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:250)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.transport.Transport$1.run(Transport.java:159)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at java.security.AccessController.doPrivileged(Native Method)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at java.lang.Thread.run(Thread.java:619)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:255)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:233)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:359)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at sun.rmi.registry.RegistryImpl_Stub.rebind(Unknown Source)
ERROR [STDERR] (ajp-localhost%2F127.0.0.1-8009-7) at java.rmi.Naming.rebind(Naming.java:160)
....

But class my.domain.webapp.MyClass_Stub is present in mywebapp.war.
What is the reason for this exception?