diff --git a/inc/init.php b/inc/init.php
index 354e0de8abd107fa4c7d5be32dd1f6c531ca5444..13fb3a4bb6cab191be9272961b7f05f25ea2dacf 100644
--- a/inc/init.php
+++ b/inc/init.php
@@ -23,6 +23,10 @@
   if (!defined('DOKU_E_LEVEL')) { error_reporting(E_ALL ^ E_NOTICE); }
   else { error_reporting(DOKU_E_LEVEL); }
 
+  // init memory caches
+  $cache_wikifn = array();
+  $cache_cleanid = array();
+
   //prepare config array()
   global $conf;
   if (!defined('DOKU_UNITTEST')) {
diff --git a/inc/pageutils.php b/inc/pageutils.php
index 882a6bf561bc667b4f54482829acc9438c52594d..758d34a9e99225c07aeb84ddb0e37a32f7cfa9ed 100644
--- a/inc/pageutils.php
+++ b/inc/pageutils.php
@@ -188,6 +188,7 @@ function wikiFN($raw_id,$rev='',$clean=true){
     }
   }
 
+  if (!isset($cache[$raw_id])) { $cache[$raw_id] = array(); }
   $cache[$raw_id][$rev] = $fn;
   return $fn;
 }