Index: sites/all/modules/cacherouter/cacherouter.inc
===================================================================
--- sites/all/modules/cacherouter/cacherouter.inc	(revision 2419)
+++ sites/all/modules/cacherouter/cacherouter.inc	(working copy)
@@ -159,7 +159,7 @@
 function page_cache_fastpath() {
   global $base_root;
   global $cache;
-  if (empty($_POST) && !$_COOKIE['cacherouter']) {
+  if (empty($_POST) && !isset($_COOKIE['cacherouter'])) {
     if (!isset($cache)) {
       $cache = new CacheRouter();
     }