Session timeout: session alive indefinitely

Hi,

I want that a session will be closed automatically if the user don't makes any activities for a while. To do that i have add to the web.xml two line (session timeout of 1 minute is only for testing, I will set this later to a higher value)

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  ...
  <context-param>
    <description>Close session if there are no user activities (after [session-timeout] minutes)</description>
    <param-name>closeIdleSessions</param-name>
    <param-value>true</param-value>
  </context-param>
  ...
  <session-config>
    <!-- adjust the session timeout (in minutes) -->
    <session-timeout>1</session-timeout>
  </session-config>
  ...
</web-app

After creating a new session and waiting for more as ten minutes the session is still open and wasn't invalidated... Is there something missing?

Thanks,
Steffen