diff --git a/change_log.txt b/change_log.txt
index 3db75cab..fde5f333 100644
--- a/change_log.txt
+++ b/change_log.txt
@@ -6,6 +6,7 @@
   - move $smarty->getTemplateVars() into extension
   - move getStreamVariable() into extension
   - move $smarty->append() and $smarty->appendByRef() into extension
+  - optimize autoloader
 
  27.06.2015
   - bugfix resolve naming conflict between custom Smarty delimiter '<%' and PHP ASP tags https://github.com/smarty-php/smarty/issues/64
diff --git a/libs/Autoloader.php b/libs/Autoloader.php
index 21a9a6bb..9bb71079 100644
--- a/libs/Autoloader.php
+++ b/libs/Autoloader.php
@@ -45,48 +45,21 @@ class Smarty_Autoloader
      *
      * @var array
      */
-    public static $rootClasses = array('Smarty' => 'Smarty.class.php', 'SmartyBC' => 'SmartyBC.class.php',);
+    public static $rootClasses = array('smarty' => 'Smarty.class.php', 'smartybc' => 'SmartyBC.class.php',);
 
-    private static $syspluginsClasses = array('smarty_config_source'                     => true,
-                                              'smarty_security'                          => true,
-                                              'smarty_cacheresource'                     => true,
-                                              'smarty_compiledresource'                  => true,
-                                              'smarty_cacheresource_custom'              => true,
-                                              'smarty_cacheresource_keyvaluestore'       => true,
-                                              'smarty_resource'                          => true,
-                                              'smarty_resource_custom'                   => true,
-                                              'smarty_resource_uncompiled'               => true,
-                                              'smarty_resource_recompiled'               => true,
-                                              'smarty_template_source'                   => true,
-                                              'smarty_template_compiled'                 => true,
-                                              'smarty_template_cached'                   => true,
-                                              'smarty_template_config'                   => true,
-                                              'smarty_data'                              => true,
-                                              'smarty_variable'                          => true,
-                                              'smarty_undefined_variable'                => true,
-                                              'smartyexception'                          => true,
-                                              'smartycompilerexception'                  => true,
-                                              'smarty_internal_data'                     => true,
-                                              'smarty_internal_template'                 => true,
-                                              'smarty_internal_templatebase'             => true,
-                                              'smarty_internal_resource_file'            => true,
-                                              'smarty_internal_resource_extends'         => true,
-                                              'smarty_internal_resource_eval'            => true,
-                                              'smarty_internal_resource_string'          => true,
-                                              'smarty_internal_resource_registered'      => true,
-                                              'smarty_internal_extension_codeframe'      => true,
-                                              'smarty_internal_extension_config'         => true,
-                                              'smarty_internal_extension_filter'         => true,
-                                              'smarty_internal_extension_autoloadfilter' => true,
-                                              'smarty_internal_extension_object'         => true,
-                                              'smarty_internal_extension_loadplugin'     => true,
-                                              'smarty_internal_extension_clearcompiled'  => true,
-                                              'smarty_internal_extension_getvars'        => true,
-                                              'smarty_internal_extension_append'         => true,
-                                              'smarty_internal_filter_handler'           => true,
-                                              'smarty_internal_function_call_handler'    => true,
-                                              'smarty_internal_cacheresource_file'       => true,
-                                              'smarty_internal_write_file'               => true,);
+    /**
+     * Array of often auto loaded classes which may skip is_file() test
+     *
+     * @var array
+     */
+    private static $classes = array('smarty_config_source'                  => true, 'smarty_security' => true,
+                                    'smarty_cacheresource'                  => true, 'smarty_compiledresource' => true,
+                                    'smarty_template_config'                => true, 'smarty_internal_data' => true,
+                                    'smarty_internal_extension_config'      => true,
+                                    'smarty_internal_extension_loadplugin'  => true,
+                                    'smarty_internal_extension_append'      => true,
+                                    'smarty_internal_filter_handler'        => true,
+                                    'smarty_internal_function_call_handler' => true,);
 
     /**
      * Registers Smarty_Autoloader backward compatible to older installations.
@@ -101,7 +74,7 @@ class Smarty_Autoloader
         if (!defined('SMARTY_SPL_AUTOLOAD')) {
             define('SMARTY_SPL_AUTOLOAD', 0);
         }
-        if (SMARTY_SPL_AUTOLOAD && set_include_path(get_include_path() . PATH_SEPARATOR . SMARTY_SYSPLUGINS_DIR) !== false) {
+        if (SMARTY_SPL_AUTOLOAD && set_include_path(get_include_path() . DIRECTORY_SEPARATOR . SMARTY_SYSPLUGINS_DIR) !== false) {
             $registeredAutoLoadFunctions = spl_autoload_functions();
             if (!isset($registeredAutoLoadFunctions['spl_autoload'])) {
                 spl_autoload_register();
@@ -118,17 +91,20 @@ class Smarty_Autoloader
      */
     public static function register($prepend = false)
     {
-        self::$SMARTY_DIR = defined('SMARTY_DIR') ? SMARTY_DIR : dirname(__FILE__) . '/';
-        self::$SMARTY_SYSPLUGINS_DIR = defined('SMARTY_SYSPLUGINS_DIR') ? SMARTY_SYSPLUGINS_DIR : self::$SMARTY_DIR . 'sysplugins/';
+        self::$SMARTY_DIR = defined('SMARTY_DIR') ? SMARTY_DIR : dirname(__FILE__) . DIRECTORY_SEPARATOR;
+        self::$SMARTY_SYSPLUGINS_DIR = defined('SMARTY_SYSPLUGINS_DIR') ? SMARTY_SYSPLUGINS_DIR : self::$SMARTY_DIR . 'sysplugins' . DIRECTORY_SEPARATOR;
         if (version_compare(phpversion(), '5.3.0', '>=')) {
             spl_autoload_register(array(__CLASS__, 'autoload'), true, $prepend);
         } else {
             spl_autoload_register(array(__CLASS__, 'autoload'));
         }
+        foreach (self::$rootClasses as $class => $file) {
+            self::$classes[$class] = self::$SMARTY_DIR . $file;
+        }
     }
 
     /**
-     * Handles autoloading of classes.
+     * Handles auto loading of classes.
      *
      * @param string $class A class name.
      */
@@ -139,19 +115,10 @@ class Smarty_Autoloader
             return;
         }
         $_class = strtolower($class);
-        if (isset(self::$syspluginsClasses[$_class])) {
-            $_class = (self::$syspluginsClasses[$_class] === true) ? $_class : self::$syspluginsClasses[$_class];
-            $file = self::$SMARTY_SYSPLUGINS_DIR . $_class . '.php';
+        if (isset(self::$classes[$_class])) {
+            $file = self::$classes[$_class] === true ? self::$SMARTY_SYSPLUGINS_DIR . $_class . '.php' : self::$classes[$_class];
             require_once $file;
             return;
-        } elseif (0 !== strpos($_class, 'smarty_internal_')) {
-            if (isset(self::$rootClasses[$class])) {
-                $file = self::$SMARTY_DIR . self::$rootClasses[$class];
-                require_once $file;
-                return;
-            }
-            self::$unknown[$class] = true;
-            return;
         }
         $file = self::$SMARTY_SYSPLUGINS_DIR . $_class . '.php';
         if (is_file($file)) {
diff --git a/libs/Smarty.class.php b/libs/Smarty.class.php
index 11fd8ae2..2334032c 100644
--- a/libs/Smarty.class.php
+++ b/libs/Smarty.class.php
@@ -111,7 +111,7 @@ class Smarty extends Smarty_Internal_TemplateBase
     /**
      * smarty version
      */
-    const SMARTY_VERSION = '3.1.28-dev/16';
+    const SMARTY_VERSION = '3.1.28-dev/17';
 
     /**
      * define variable scopes