2.1 demo site: /civicrm/mailing/subscribe returns "Could not find valid Key"

There seems to be an issue with the 2.1 demo site for the URL: http://drupal.demo.civicrm.org/civicrm/mailing/subscribe?reset=1

I enter in an email address and check "Newsletter Subscribers" and then click the Subscribe button. I am then redirected to an non-recoverable error page with that says "Could not find valid Key". Maybe this isn't even an issue, and is due to something in the testing environment, but it seems like it should at the very least take you to a success page of some sort, even though an actual email is never sent out.