I disagree. The specification only says immutable but does not say what is supposed to happen when somebody _tries_ to modify it. Throwing an UnsupportedOperationException is in my opinion reasonable. I haven't actually checked what the RI does but silently ignoring the attempt to add a request parameter is surely not an option. If if the error was swallowed because whatever Icefaces is trying to achieve by putting the viewNumber into the map would ot be achieved. So this is definitly a bug in Icefaces and this is one more reason why I would not recommend it. Regards Felix View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4003068#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...