Context.User gives NullReferenceException on rewritten URLs

Edit: My mistake...I forgot to set runAllManagedModulesForAllRequests to true in my web.config
 
Hello,
When I use something like Context.User.Identity.IsAuthenticated on page that has its URL rewritten I get an "Object reference not set to an instance of an object." error.
Everything works fine if I access the page using the original URL.
Any advice on how to handle this would be appreciated.
Thank you~

 
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