Cannot store reference to a stateful session bean in the HTTP session

I have ported an application from AS 5/EAP 5.1 to AS 7 (a snapshot of Beta 2 actually), and in that application I am looking up a reference to a stateful session bean, to store it in the HTTP session, and the actual storage of the reference, gets the following:

javax.servlet.ServletException: java.lang.IllegalArgumentException: setAttribute: Non-serializable attribute sfsbOrderInquiry
services.web.OrderInquiryServlet.doGet(OrderInquiryServlet.java:78)
javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
javax.servlet.http.HttpServlet.service(HttpServlet.java:847)

root cause

java.lang.IllegalArgumentException: setAttribute: Non-serializable attribute sfsbOrderInquiry
org.apache.catalina.session.StandardSession.setAttribute(StandardSession.java:1289)
org.apache.catalina.session.StandardSession.setAttribute(StandardSession.java:1250)
org.apache.catalina.session.StandardSessionFacade.setAttribute(StandardSessionFacade.java:130)
services.web.OrderInquiryServlet.doGet(OrderInquiryServlet.java:74)
javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
javax.servlet.http.HttpServlet.service(HttpServlet.java:847)

It's saying that my attribute is not serializable, but the OrderInquiryBean in the lookup implements Serializable.

The code in the servlet is as such, and it fails on the session.setAttribute("sfsbOrderInquiry", orderInquiry):

HttpSession session = request.getSession();

OrderInquiry orderInquiry = (OrderInquiry) session.getAttribute("sfsbOrderInquiry");

if (orderInquiry == null) {

InitialContext context = null;

try

{ context = new InitialContext(); orderInquiry = (OrderInquiry) context.lookup("java:app/OrderManagerEJB/OrderInquiryBean!services.ejb.OrderInquiry"); session.setAttribute("sfsbOrderInquiry", orderInquiry); }

catch(Exception lookupError)

{ logger.log(Level.ERROR, lookupError.getStackTrace().toString()); response.setStatus(500); throw new ServletException(lookupError); }

}

The top of OrderInquireBean looks like:

@Stateful
public class OrderInquiryBean implements OrderInquiry, Serializable {

/** The serialVersionUID */
private static final long serialVersionUID = -9113338082170911949L