diff --git a/system/src/Grav/Common/Config.php b/system/src/Grav/Common/Config.php
index b8a646fe1..e467ab8b9 100644
--- a/system/src/Grav/Common/Config.php
+++ b/system/src/Grav/Common/Config.php
@@ -55,7 +55,7 @@ class Config extends Data
     {
         // Build file map.
         $files = $this->build();
-        $key = md5(serialize($files) . GRAV_VERSION);
+        $key = md5(json_encode($files) . GRAV_VERSION);
 
         if ($force || $key != $this->key) {
             // First take non-blocking lock to the file.
diff --git a/system/src/Grav/Common/Page/Pages.php b/system/src/Grav/Common/Page/Pages.php
index fb45bc897..dda35ef01 100644
--- a/system/src/Grav/Common/Page/Pages.php
+++ b/system/src/Grav/Common/Page/Pages.php
@@ -173,7 +173,7 @@ class Pages
     {
         $items = $collection->toArray();
 
-        $lookup = md5(serialize($items));
+        $lookup = md5(json_encode($items));
         if (!isset($this->sort[$lookup][$orderBy])) {
             $this->buildSort($lookup, $items, $orderBy, $orderManual);
         }
diff --git a/system/src/Grav/Common/TwigExtension.php b/system/src/Grav/Common/TwigExtension.php
index 7cb241bb9..9cfff0a83 100644
--- a/system/src/Grav/Common/TwigExtension.php
+++ b/system/src/Grav/Common/TwigExtension.php
@@ -126,7 +126,8 @@ class TwigExtension extends \Twig_Extension
         $random = array_slice($original, $offset);
         shuffle($random);
 
-        for ($x=0; $x < sizeof($original); $x++) {
+        $sizeOf = sizeof($original);
+        for ($x=0; $x < $sizeOf; $x++) {
             if ($x < $offset) {
                 $sorted[] = $original[$x];
             } else {