diff --git a/core/lib/Drupal/Core/Template/Loader/ThemeRegistryLoader.php b/core/lib/Drupal/Core/Template/Loader/ThemeRegistryLoader.php
index fe1ae25..7f74cb0 100644
--- a/core/lib/Drupal/Core/Template/Loader/ThemeRegistryLoader.php
+++ b/core/lib/Drupal/Core/Template/Loader/ThemeRegistryLoader.php
@@ -38,6 +38,8 @@ public function __construct(Registry $theme_registry) {
    *
    * @param string $name
    *   The name of the template to load.
+   * @param bool $throw
+   *   Whether to throw an exception when an error occurs
    *
    * @return string
    *   The path to the template.
@@ -45,7 +47,7 @@ public function __construct(Registry $theme_registry) {
    * @throws \Twig_Error_Loader
    *   Thrown if a template matching $name cannot be found.
    */
-  protected function findTemplate($name) {
+  protected function findTemplate($name, $throw = TRUE) {
     // Allow for loading based on the Drupal theme registry.
     $hook = str_replace('.html.twig', '', strtr($name, '-', '_'));
     $theme_registry = $this->themeRegistry->getRuntime();
@@ -63,7 +65,9 @@ protected function findTemplate($name) {
       }
     }
 
-    throw new \Twig_Error_Loader(sprintf('Unable to find template "%s" in the Drupal theme registry.', $name));
+    if ($throw) {
+      throw new \Twig_Error_Loader(sprintf('Unable to find template "%s" in the Drupal theme registry.', $name));
+    }
   }
 
 }
diff --git a/core/lib/Drupal/Core/Template/TwigEnvironment.php b/core/lib/Drupal/Core/Template/TwigEnvironment.php
index 2deec5f..058e13f 100644
--- a/core/lib/Drupal/Core/Template/TwigEnvironment.php
+++ b/core/lib/Drupal/Core/Template/TwigEnvironment.php
@@ -28,6 +28,8 @@ class TwigEnvironment extends \Twig_Environment {
    */
   protected $templateClasses;
 
+  protected $templateClassPrefix = '__TwigTemplate_';
+
   /**
    * Constructs a TwigEnvironment object and stores cache and storage
    * internally.
diff --git a/core/lib/Drupal/Core/Template/TwigNodeTrans.php b/core/lib/Drupal/Core/Template/TwigNodeTrans.php
index a7b723a..fe2753a 100644
--- a/core/lib/Drupal/Core/Template/TwigNodeTrans.php
+++ b/core/lib/Drupal/Core/Template/TwigNodeTrans.php
@@ -25,7 +25,7 @@ class TwigNodeTrans extends \Twig_Node {
   /**
    * {@inheritdoc}
    */
-  public function __construct(\Twig_NodeInterface $body, \Twig_NodeInterface $plural = NULL, \Twig_Node_Expression $count = NULL, \Twig_Node_Expression $options = NULL, $lineno, $tag = NULL) {
+  public function __construct(\Twig_Node $body, \Twig_Node $plural = NULL, \Twig_Node_Expression $count = NULL, \Twig_Node_Expression $options = NULL, $lineno, $tag = NULL) {
     parent::__construct(array(
       'count' => $count,
       'body' => $body,
@@ -91,7 +91,7 @@ public function compile(\Twig_Compiler $compiler) {
   /**
    * Extracts the text and tokens for the "trans" tag.
    *
-   * @param \Twig_NodeInterface $body
+   * @param \Twig_Node $body
    *   The node to compile.
    *
    * @return array
@@ -101,7 +101,7 @@ public function compile(\Twig_Compiler $compiler) {
    *   - array $tokens
    *       The extracted tokens as new \Twig_Node_Expression_Name instances.
    */
-  protected function compileString(\Twig_NodeInterface $body) {
+  protected function compileString(\Twig_Node $body) {
     if ($body instanceof \Twig_Node_Expression_Name || $body instanceof \Twig_Node_Expression_Constant || $body instanceof \Twig_Node_Expression_TempName) {
       return array($body, array());
     }
diff --git a/core/lib/Drupal/Core/Template/TwigNodeVisitor.php b/core/lib/Drupal/Core/Template/TwigNodeVisitor.php
index ac1e676..860cc56 100644
--- a/core/lib/Drupal/Core/Template/TwigNodeVisitor.php
+++ b/core/lib/Drupal/Core/Template/TwigNodeVisitor.php
@@ -16,19 +16,19 @@
  *
  * @see twig_render
  */
-class TwigNodeVisitor implements \Twig_NodeVisitorInterface {
+class TwigNodeVisitor extends \Twig_BaseNodeVisitor {
 
   /**
    * {@inheritdoc}
    */
-  public function enterNode(\Twig_NodeInterface $node, \Twig_Environment $env) {
+  protected function doEnterNode(\Twig_Node $node, \Twig_Environment $env) {
     return $node;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function leaveNode(\Twig_NodeInterface $node, \Twig_Environment $env) {
+  protected function doLeaveNode(\Twig_Node $node, \Twig_Environment $env) {
     // We use this to inject a call to render_var -> TwigExtension->renderVar()
     // before anything is printed.
     if ($node instanceof \Twig_Node_Print) {
diff --git a/core/lib/Drupal/Core/Template/TwigTransTokenParser.php b/core/lib/Drupal/Core/Template/TwigTransTokenParser.php
index c67f463..009cc9c 100644
--- a/core/lib/Drupal/Core/Template/TwigTransTokenParser.php
+++ b/core/lib/Drupal/Core/Template/TwigTransTokenParser.php
@@ -82,14 +82,14 @@ public function getTag() {
   /**
    * Ensure that any nodes that are parsed are only of allowed types.
    *
-   * @param \Twig_NodeInterface $body
+   * @param \Twig_Node $body
    *   The expression to check.
    * @param integer $lineno
    *   The source line.
    *
    * @throws \Twig_Error_Syntax
    */
-  protected function checkTransString(\Twig_NodeInterface $body, $lineno) {
+  protected function checkTransString(\Twig_Node $body, $lineno) {
     foreach ($body as $node) {
       if (
         $node instanceof \Twig_Node_Text
diff --git a/core/modules/system/tests/modules/twig_extension_test/src/TwigExtension/TestExtension.php b/core/modules/system/tests/modules/twig_extension_test/src/TwigExtension/TestExtension.php
index 3c2b851..c4c6025 100644
--- a/core/modules/system/tests/modules/twig_extension_test/src/TwigExtension/TestExtension.php
+++ b/core/modules/system/tests/modules/twig_extension_test/src/TwigExtension/TestExtension.php
@@ -12,7 +12,7 @@
 /**
  * A test Twig extension that adds a custom function and a custom filter.
  */
-class TestExtension extends TwigExtension {
+class TestExtension extends \Twig_Extension {
 
   /**
    * Generates a list of all Twig functions that this extension defines.
@@ -27,9 +27,9 @@ class TestExtension extends TwigExtension {
    *   The value is a standard PHP callback that defines what the function does.
    */
   public function getFunctions() {
-    return array(
-      'testfunc' => new \Twig_Function_Function(array('Drupal\twig_extension_test\TwigExtension\TestExtension', 'testFunction')),
-    );
+    return [
+      new \Twig_SimpleFunction('testfunc', [$this, 'testFunction']),
+    ];
   }
 
   /**
@@ -45,9 +45,9 @@ public function getFunctions() {
    *   The value is a standard PHP callback that defines what the filter does.
    */
   public function getFilters() {
-    return array(
-      'testfilter' => new \Twig_Filter_Function(array('Drupal\twig_extension_test\TwigExtension\TestExtension', 'testFilter')),
-    );
+    return [
+      new \Twig_SimpleFilter('testfilter', [$this, 'testFilter']),
+    ];
   }
 
   /**
diff --git a/core/modules/system/tests/modules/twig_extension_test/twig_extension_test.services.yml b/core/modules/system/tests/modules/twig_extension_test/twig_extension_test.services.yml
index 491d1e8..8784c0f 100644
--- a/core/modules/system/tests/modules/twig_extension_test/twig_extension_test.services.yml
+++ b/core/modules/system/tests/modules/twig_extension_test/twig_extension_test.services.yml
@@ -1,6 +1,5 @@
 services:
   twig_extension_test.twig.test_extension:
-    arguments: ['@renderer']
     class: Drupal\twig_extension_test\TwigExtension\TestExtension
     tags:
       - { name: twig.extension }
diff --git a/core/tests/Drupal/Tests/Core/Template/AttributeTest.php b/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
index b4a192d..7060401 100644
--- a/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
+++ b/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
@@ -10,6 +10,7 @@
 use Drupal\Core\Template\Attribute;
 use Drupal\Core\Template\AttributeArray;
 use Drupal\Core\Template\AttributeString;
+use Drupal\Core\Template\Loader\StringLoader;
 use Drupal\Tests\UnitTestCase;
 
 /**
@@ -253,7 +254,7 @@ public function testChainAddRemoveClasses() {
    * @covers ::addClass
    */
   public function testTwigAddRemoveClasses($template, $expected, $seed_attributes = array()) {
-    $loader = new \Twig_Loader_String();
+    $loader = new StringLoader();
     $twig = new \Twig_Environment($loader);
     $data = array('attributes' => new Attribute($seed_attributes));
     $result = $twig->render($template, $data);
diff --git a/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php b/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
index 3e78e91..7d55719 100644
--- a/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
+++ b/core/tests/Drupal/Tests/Core/Template/TwigExtensionTest.php
@@ -12,6 +12,7 @@
 use Drupal\Core\Render\RendererInterface;
 use Drupal\Core\Template\TwigEnvironment;
 use Drupal\Core\Template\TwigExtension;
+use Drupal\Core\Template\Loader\StringLoader;
 use Drupal\Tests\UnitTestCase;
 
 /**
@@ -30,7 +31,8 @@ class TwigExtensionTest extends UnitTestCase {
    */
   public function testEscaping($template, $expected) {
     $renderer = $this->getMock('\Drupal\Core\Render\RendererInterface');
-    $twig = new \Twig_Environment(NULL, array(
+    $loader = new \Twig_Loader_Filesystem();
+    $twig = new \Twig_Environment($loader, array(
       'debug' => TRUE,
       'cache' => FALSE,
       'autoescape' => 'html',
@@ -96,7 +98,7 @@ public function testActiveTheme() {
       ->willReturn($active_theme);
     $extension->setThemeManager($theme_manager);
 
-    $loader = new \Twig_Loader_String();
+    $loader = new StringLoader();
     $twig = new \Twig_Environment($loader);
     $twig->addExtension($extension);
     $result = $twig->render('{{ active_theme() }}');
@@ -110,7 +112,8 @@ public function testActiveTheme() {
    */
   public function testSafeStringEscaping() {
     $renderer = $this->getMock('\Drupal\Core\Render\RendererInterface');
-    $twig = new \Twig_Environment(NULL, array(
+    $loader = new \Twig_Loader_Filesystem();
+    $twig = new \Twig_Environment($loader, array(
       'debug' => TRUE,
       'cache' => FALSE,
       'autoescape' => 'html',