--- a/index.cgi	Thu Jul 07 22:28:08 2011 +0200
+++ b/index.cgi	Thu Jul 07 22:28:41 2011 +0200
@@ -308,7 +308,9 @@
 
 		$sent = param("email");
 	    }
-	    print redirect("$SELF/done/invitation?email=" . _encrypt($sent));
+	    print redirect("$SELF/done/invitation"
+			. "?email=" . _encrypt($sent)
+			. ";expires=" . _encrypt($EXPIRATION));
 	    exit 0;
 	}