Error validating web.xml when session-timeout=-1

Hi,
  I am trying to use session-timeout with value of -1 since my web application
should never expire. Though this change in web.xml works at runtime but when i
try to prepare the war using ant and validate the web.xml against the DTD i see
following exception:

compile_war:
     [move] Moving 1 file to
D:\dev\depot\lanai\appsvcs-ui-oahu.all\ptree\weblogic\wars
     [java] [appc] Created working directory:
D:\dev\depot\lanai\appsvcs-ui-oahu.all\build\javatmpdir\appcgen
     [java] [JspcInvoker]Checking web app for compliance.
     [java] <May 31, 2007 7:58:38 PM IST> <Info> <HTTP>
<BEA-101047> <[ComplianceChecker] Validating the servlet element with
servlet-name named "dispatcher".>
     [java] <May 31, 2007 7:58:39 PM IST> <Info> <HTTP>
<BEA-101047> <[ComplianceChecker] Checking servlet-mapping for servlet
name : "dispatcher".>
     [java] [J2EE:160119]Appc is unable to process the file
'D:\dev\depot\lanai\appsvcs-ui-oahu.all\ptree\weblogic\wars\vgn-configconsole.wa
r_temp.war'. The following error occurred:

     [java] The session-timeout in minutes must be -2 to use the global server
timeout for WebLogic sessions. Otherwise, it must be greater than zero, not
"-1"".

     [java]     at
weblogic.servlet.internal.dd.compliance.ComplianceUtils.checkCompliance(Complian
ceUtils.java:47)
     [java]     at
weblogic.servlet.jsp.JspcInvoker.compile(JspcInvoker.java:139)
     [java]     at weblogic.appc.compileWAR(appc.java:866)
     [java]     at weblogic.appc.compileWAR(appc.java:822)
     [java]     at weblogic.appc.compileInput(appc.java:472)
     [java]     at weblogic.appc.runBody(appc.java:186)
     [java]     at weblogic.utils.compiler.Tool.run(Tool.java:192)
     [java]     at weblogic.utils.compiler.Tool.run(Tool.java:147)
     [java]     at weblogic.appc.main(appc.java:1037)

     [java] weblogic.servlet.internal.dd.compliance.ComplianceException: The
session-timeout in minutes must be -2 to use the global server timeout for
WebLogic sessions. Otherwise, it must be greater than zero, not
"-1"".
     [java]     at
weblogic.servlet.internal.dd.compliance.BaseComplianceChecker.addDescriptorError
(BaseComplianceChecker.java:75)
     [java]     at
weblogic.servlet.internal.dd.compliance.BaseComplianceChecker.addDescriptorError
(BaseComplianceChecker.java:81)
     [java]     at
weblogic.servlet.internal.dd.compliance.WebAppDescriptorComplianceChecker.valida
teSessionConfig(WebAppDescriptorComplianceChecker.java:88)
     [java]     at
weblogic.servlet.internal.dd.compliance.WebAppDescriptorComplianceChecker.check(
WebAppDescriptorComplianceChecker.java:63)
     [java]     at
weblogic.servlet.internal.dd.compliance.ComplianceUtils.checkCompliance(Complian
ceUtils.java:45)
     [java]     at
weblogic.servlet.jsp.JspcInvoker.compile(JspcInvoker.java:139)
     [java]     at weblogic.appc.compileWAR(appc.java:866)
     [java]     at weblogic.appc.compileWAR(appc.java:822)
     [java]     at weblogic.appc.compileInput(appc.java:472)
     [java]     at weblogic.appc.runBody(appc.java:186)
     [java]     at weblogic.utils.compiler.Tool.run(Tool.java:192)
     [java]     at weblogic.utils.compiler.Tool.run(Tool.java:147)
     [java]     at weblogic.appc.main(appc.java:1037)


Please let me know how to overcome this issue.

Thanks