diff --git a/classes/Autoload.php b/classes/Autoload.php
index b9b5a394e..903484add 100644
--- a/classes/Autoload.php
+++ b/classes/Autoload.php
@@ -137,24 +137,18 @@ class Autoload
 
 		// Write classes index on disc to cache it
 		$filename = $this->root_dir.Autoload::INDEX_FILE;
-		if ((file_exists($filename) && !is_writable($filename)) || !is_writable(dirname($filename)))
+		$filename_tmp = tempnam(dirname($filename), basename($filename.'.'));
+		if ($filename_tmp !== false && file_put_contents($filename_tmp, $content, LOCK_EX) !== false)
 		{
-			header('HTTP/1.1 503 temporarily overloaded');
-			// Cannot use PrestaShopException in this context
-			die('/cache/class_index.php is not writable, please give write permissions (chmod 666) on this file.');
-		}
-		else
-		{
-			$filename_tmp = tempnam(dirname($filename), basename($filename.'.'));
-			if($filename_tmp !== FALSE and file_put_contents($filename_tmp, $content, LOCK_EX) !== FALSE)
-			{
-				@rename($filename_tmp, $filename);
-				@chmod($filename, 0666);
-			}
+			if (!rename($filename_tmp, $filename))
+				unlink($filename_tmp);
 			else
-				// $filename_tmp couldn't be written. $filename should be there anyway (even if outdated), no need to die.
-				error_log('Cannot write temporary file '.$filename_tmp);
+				@chmod($filename, 0666);
 		}
+		// $filename_tmp couldn't be written. $filename should be there anyway (even if outdated), no need to die.
+		else
+			error_log('Cannot write temporary file '.$filename_tmp);
+
 		$this->index = $classes;
 	}
 
diff --git a/classes/Hook.php b/classes/Hook.php
index 30efb0a76..656934e16 100644
--- a/classes/Hook.php
+++ b/classes/Hook.php
@@ -390,6 +390,10 @@ class HookCore extends ObjectModel
 	 */
 	public static function exec($hook_name, $hook_args = array(), $id_module = null, $array_return = false, $check_exceptions = true)
 	{
+		static $disable_non_native_modules = null;
+		if ($disable_non_native_modules === null)
+			$disable_non_native_modules = (bool)Configuration::get('PS_DISABLE_NON_NATIVE_MODULE');
+
 		// Check arguments validity
 		if (($id_module && !is_numeric($id_module)) || !Validate::isHookName($hook_name))
 			throw new PrestaShopException('Invalid id_module or hook_name');
@@ -419,7 +423,7 @@ class HookCore extends ObjectModel
 		$altern = 0;
 		$output = '';
 
-		if (!isset(Hook::$native_module))
+		if ($disable_non_native_modules && !isset(Hook::$native_module))
 			Hook::$native_module = Module::getNativeModuleList();
 
 		foreach ($module_list as $array)
@@ -428,7 +432,7 @@ class HookCore extends ObjectModel
 			if ($id_module && $id_module != $array['id_module'])
 				continue;
 
-			if ((bool)Configuration::get('PS_DISABLE_NON_NATIVE_MODULE') && !in_array($array['module'], self::$native_module))
+			if ((bool)$disable_non_native_modules && Hook::$native_module && count(Hook::$native_module) && !in_array($array['module'], self::$native_module))
 				continue;
 
 			if (!($moduleInstance = Module::getInstanceByName($array['module'])))
diff --git a/classes/module/Module.php b/classes/module/Module.php
index 3318ca9e4..dea6881fc 100644
--- a/classes/module/Module.php
+++ b/classes/module/Module.php
@@ -1296,6 +1296,9 @@ abstract class ModuleCore
 	public static function getNativeModuleList()
 	{
 		$module_list_xml = _PS_ROOT_DIR_.self::CACHE_FILE_MODULES_LIST;
+		if (!file_exists($module_list_xml))
+			return false;
+
 		$native_modules = simplexml_load_file($module_list_xml);
 		$native_modules = $native_modules->modules;
 		$modules = array();