EJBContext.getCallerPrincipal() results in IllegalStateException

Observed behavior:

calling EJBContext.getCallerPrincipal() for not logged-in user (Stateless bean method invoked from non-secure servlet) results in java.lang.IllegalStateException: No valid security context for the caller identity exception.

Stateless bean definition follows:

@Stateless(name = "AwardService")
@SecurityDomain(unauthenticatedPrincipal = "guest", value = "portal")
public class AwardServiceImpl implements AwardService {
.....
}

Expected behavior:

"guest" principal to be returned on getCallerPrincipal() method invocation.