diff --git a/libs/Autoloader.php b/libs/Autoloader.php
index ad09ec29..0b794804 100644
--- a/libs/Autoloader.php
+++ b/libs/Autoloader.php
@@ -11,7 +11,7 @@
  * @package    Smarty
  * @author     Uwe Tews
  *             Usage:
- *             include '...path/Autoloader.php';
+ *             require_once '...path/Autoloader.php';
  *             Smarty_Autoloader::register();
  *             $smarty = new Smarty();
  *             Note:       This autoloader is not needed if you use Composer.
@@ -47,24 +47,38 @@ class Smarty_Autoloader
     );
 
     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_data'                        => true,
-        'smarty_variable'                    => true,
-        'smarty_undefined_variable'          => true,
-        'smartyexception'                    => true,
-        'smartycompilerexception'            => true,
+        '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_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_filter_handler'        => true,
+        'smarty_internal_function_call_handler' => true,
+        'smarty_internal_cacheresource_file'    => true,
+        'smarty_internal_write_file'    => true,
     );
 
     /**
@@ -121,12 +135,12 @@ class Smarty_Autoloader
         if (isset(self::$syspluginsClasses[$_class])) {
             $_class = (self::$syspluginsClasses[$_class] === true) ? $_class : self::$syspluginsClasses[$_class];
             $file = self::$SMARTY_SYSPLUGINS_DIR . $_class . '.php';
-            require $file;
+            require_once $file;
             return;
         } elseif (0 !== strpos($_class, 'smarty_internal_')) {
             if (isset(self::$rootClasses[$class])) {
                 $file = self::$SMARTY_DIR . self::$rootClasses[$class];
-                require $file;
+                require_once $file;
                 return;
             }
             self::$unknown[$class] = true;
@@ -134,7 +148,7 @@ class Smarty_Autoloader
         }
         $file = self::$SMARTY_SYSPLUGINS_DIR . $_class . '.php';
         if (is_file($file)) {
-            require $file;
+            require_once $file;
             return;
         }
         self::$unknown[$class] = true;
diff --git a/libs/plugins/modifier.date_format.php b/libs/plugins/modifier.date_format.php
index 5ad7540b..28d6ff02 100644
--- a/libs/plugins/modifier.date_format.php
+++ b/libs/plugins/modifier.date_format.php
@@ -33,7 +33,7 @@ function smarty_modifier_date_format($string, $format = null, $default_date = ''
         $format = Smarty::$_DATE_FORMAT;
     }
     /**
-     * Include the {@link shared.make_timestamp.php} plugin
+     * require_once the {@link shared.make_timestamp.php} plugin
      */
     require_once(SMARTY_PLUGINS_DIR . 'shared.make_timestamp.php');
     if ($string != '' && $string != '0000-00-00' && $string != '0000-00-00 00:00:00') {
diff --git a/libs/sysplugins/smarty_internal_compile_function.php b/libs/sysplugins/smarty_internal_compile_function.php
index 3366910b..07bc0899 100644
--- a/libs/sysplugins/smarty_internal_compile_function.php
+++ b/libs/sysplugins/smarty_internal_compile_function.php
@@ -141,7 +141,7 @@ class Smarty_Internal_Compile_Functionclose extends Smarty_Internal_CompileBase
             if (!empty($compiler->template->required_plugins['compiled'])) {
                 foreach ($compiler->template->required_plugins['compiled'] as $tmp) {
                     foreach ($tmp as $data) {
-                        $output .= "if (!is_callable('{$data['function']}')) include '{$data['file']}';\n";
+                        $output .= "if (!is_callable('{$data['function']}')) require_once '{$data['file']}';\n";
                     }
                 }
             }
@@ -149,7 +149,7 @@ class Smarty_Internal_Compile_Functionclose extends Smarty_Internal_CompileBase
                 $output .= "echo '/*%%SmartyNocache:{$compiler->template->properties['nocache_hash']}%%*/<?php ";
                 foreach ($compiler->template->required_plugins['nocache'] as $tmp) {
                     foreach ($tmp as $data) {
-                        $output .= "if (!is_callable(\'{$data['function']}\')) include \'{$data['file']}\';\n";
+                        $output .= "if (!is_callable(\'{$data['function']}\')) require_once \'{$data['file']}\';\n";
                     }
                 }
                 $output .= "?>/*/%%SmartyNocache:{$compiler->template->properties['nocache_hash']}%%*/';\n";
@@ -185,7 +185,7 @@ class Smarty_Internal_Compile_Functionclose extends Smarty_Internal_CompileBase
         if (!empty($compiler->template->required_plugins['compiled'])) {
             foreach ($compiler->template->required_plugins['compiled'] as $tmp) {
                 foreach ($tmp as $data) {
-                    $output .= "if (!is_callable('{$data['function']}')) include '{$data['file']}';\n";
+                    $output .= "if (!is_callable('{$data['function']}')) require_once '{$data['file']}';\n";
                 }
             }
         }
diff --git a/libs/sysplugins/smarty_internal_extension_codeframe.php b/libs/sysplugins/smarty_internal_extension_codeframe.php
index 793c2fce..cd58f37c 100644
--- a/libs/sysplugins/smarty_internal_extension_codeframe.php
+++ b/libs/sysplugins/smarty_internal_extension_codeframe.php
@@ -46,9 +46,9 @@ class Smarty_Internal_Extension_CodeFrame
                     foreach ($tmp as $data) {
                         $file = addslashes($data['file']);
                         if (is_Array($data['function'])) {
-                            $output .= "if (!is_callable(array('{$data['function'][0]}','{$data['function'][1]}'))) include '{$file}';\n";
+                            $output .= "if (!is_callable(array('{$data['function'][0]}','{$data['function'][1]}'))) require_once '{$file}';\n";
                         } else {
-                            $output .= "if (!is_callable('{$data['function']}')) include '{$file}';\n";
+                            $output .= "if (!is_callable('{$data['function']}')) require_once '{$file}';\n";
                         }
                     }
                 }
@@ -60,9 +60,9 @@ class Smarty_Internal_Extension_CodeFrame
                     foreach ($tmp as $data) {
                         $file = addslashes($data['file']);
                         if (is_Array($data['function'])) {
-                            $output .= addslashes("if (!is_callable(array('{$data['function'][0]}','{$data['function'][1]}'))) include '{$file}';\n");
+                            $output .= addslashes("if (!is_callable(array('{$data['function'][0]}','{$data['function'][1]}'))) require_once '{$file}';\n");
                         } else {
-                            $output .= addslashes("if (!is_callable('{$data['function']}')) include '{$file}';\n");
+                            $output .= addslashes("if (!is_callable('{$data['function']}')) require_once '{$file}';\n");
                         }
                     }
                 }
diff --git a/libs/sysplugins/smarty_internal_templatecompilerbase.php b/libs/sysplugins/smarty_internal_templatecompilerbase.php
index 04e538e9..fdb32017 100644
--- a/libs/sysplugins/smarty_internal_templatecompilerbase.php
+++ b/libs/sysplugins/smarty_internal_templatecompilerbase.php
@@ -701,7 +701,7 @@ abstract class Smarty_Internal_TemplateCompilerBase
                         $this->template->required_plugins['compiled'][$tag][$plugin_type]['file'] = $script;
                         $this->template->required_plugins['compiled'][$tag][$plugin_type]['function'] = $callback;
                     }
-                    include_once $script;
+                    require_once $script;
                 } else {
                     $this->trigger_template_error("Default plugin handler: Returned script file \"{$script}\" for \"{$tag}\" not found");
                 }