Stateless Session Bean getCallerPrincipal().getName() is cached between Remote Calls from Standalone Client with different User's

Calling a Stateless Session Bean with different Users from a standalone Client delivers the same Principal Name.
The roles of the different Users are correct.
Only the name of the Principal is always the name from the first invocation.

The behaivor is testet with the simple Login Module and with JAAS Login.
For code snippets see also the jboss forum reference.