max-active-sessions doesn't force min-idle sessions to passivate resulting in IllegalStateException

    <system-out>19:20:59,397 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/passivating].[org.jboss.as.test.clustering.single.web.SimpleServlet]] (http--127.0.0.1-8080-3) Servlet.service() for servlet org.jboss.as.test.clustering.single.web.SimpleServlet threw exception: java.lang.IllegalStateException: JBAS018075: Number of active sessions exceeds limit 20 trying to create session 
        at org.jboss.as.web.session.DistributableSessionManager.createSessionInternal(DistributableSessionManager.java:594) [jboss-as-web-7.1.2.Final-SNAPSHOT.jar:7.1.2.Final-SNAPSHOT]
        at org.jboss.as.web.session.DistributableSessionManager.createSession(DistributableSessionManager.java:559) [jboss-as-web-7.1.2.Final-SNAPSHOT.jar:7.1.2.Final-SNAPSHOT]
        at org.apache.catalina.connector.Request.doGetSession(Request.java:2665) [jbossweb-7.0.14.Final.jar:]
        at org.apache.catalina.connector.Request.getSession(Request.java:2375) [jbossweb-7.0.14.Final.jar:]
        at org.apache.catalina.connector.RequestFacade.getSession(RequestFacade.java:841) [jbossweb-7.0.14.Final.jar:]
        at org.jboss.as.test.clustering.single.web.SimpleServlet.doGet(SimpleServlet.java:47) [classes:]
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:734) [jboss-servlet-api_3.0_spec-1.0.1.Final.jar:1.0.1.Final]
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) [jboss-servlet-api_3.0_spec-1.0.1.Final.jar:1.0.1.Final]
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329) [jbossweb-7.0.14.Final.jar:]
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.14.Final.jar:]
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275) [jbossweb-7.0.14.Final.jar:]
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161) [jbossweb-7.0.14.Final.jar:]
        at org.jboss.modcluster.container.jbossweb.JBossWebContext$RequestListenerValve.event(JBossWebContext.java:67)
        at org.jboss.modcluster.container.jbossweb.JBossWebContext$RequestListenerValve.invoke(JBossWebContext.java:48)
        at org.jboss.as.web.session.ClusteredSessionValve.handleRequest(ClusteredSessionValve.java:125) [jboss-as-web-7.1.2.Final-SNAPSHOT.jar:7.1.2.Final-SNAPSHOT]
        at org.jboss.as.web.session.ClusteredSessionValve.invoke(ClusteredSessionValve.java:91) [jboss-as-web-7.1.2.Final-SNAPSHOT.jar:7.1.2.Final-SNAPSHOT]
        at org.jboss.as.web.session.JvmRouteValve.invoke(JvmRouteValve.java:88) [jboss-as-web-7.1.2.Final-SNAPSHOT.jar:7.1.2.Final-SNAPSHOT]
        at org.jboss.as.web.session.LockingValve.invoke(LockingValve.java:56) [jboss-as-web-7.1.2.Final-SNAPSHOT.jar:7.1.2.Final-SNAPSHOT]
        at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:153) [jboss-as-web-7.1.2.Final-SNAPSHOT.jar:7.1.2.Final-SNAPSHOT]
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155) [jbossweb-7.0.14.Final.jar:]
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [jbossweb-7.0.14.Final.jar:]
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [jbossweb-7.0.14.Final.jar:]
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368) [jbossweb-7.0.14.Final.jar:]
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877) [jbossweb-7.0.14.Final.jar:]
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:671) [jbossweb-7.0.14.Final.jar:]
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:931) [jbossweb-7.0.14.Final.jar:]
        at java.lang.Thread.run(Thread.java:662) [rt.jar:1.6.0_29]