diff --git a/core/core.services.yml b/core/core.services.yml
index c26834c..3dc14f4 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -948,7 +948,7 @@ services:
   twig.loader:
     alias: twig.loader.filesystem
   twig.loader.filesystem:
-    class: Twig_Loader_Filesystem
+    class: Drupal\Core\Template\TwigThemeRegistryLoader
     arguments: ['%app.root%']
   element_info:
     alias: plugin.manager.element_info
diff --git a/core/lib/Drupal/Core/Template/TwigThemeRegistryLoader.php b/core/lib/Drupal/Core/Template/TwigThemeRegistryLoader.php
new file mode 100644
index 0000000..acfda12
--- /dev/null
+++ b/core/lib/Drupal/Core/Template/TwigThemeRegistryLoader.php
@@ -0,0 +1,75 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Template\TwigThemeRegistryLoader.
+ */
+
+namespace Drupal\Core\Template;
+
+/**
+ * Registers paths based on information from the Drupal theme registry.
+ *
+ * Allows for template inheritance based on the currently active template.
+ *
+ * @see \Drupal\Core\CoreServiceProvider
+ */
+class TwigThemeRegistryLoader extends \Twig_Loader_Filesystem {
+
+  /**
+   * @todo Docblock!
+   */
+  protected function findTemplate($name) {
+    $name = (string) $name;
+
+    // Normalize name.
+    $name = preg_replace('#/{2,}#', '/', strtr($name, '\\', '/'));
+
+    if (isset($this->cache[$name])) {
+      return $this->cache[$name];
+    }
+
+    $this->validateName($name);
+
+    $namespace = self::MAIN_NAMESPACE;
+    $shortname = $name;
+    if (isset($name[0]) && '@' == $name[0]) {
+      if (false === $pos = strpos($name, '/')) {
+        throw new \Twig_Error_Loader(sprintf('Malformed namespaced template name "%s" (expecting "@namespace/template_name").', $name));
+      }
+
+      $namespace = substr($name, 1, $pos - 1);
+      $shortname = substr($name, $pos + 1);
+    }
+
+    if (!isset($this->paths[$namespace])) {
+      throw new \Twig_Error_Loader(sprintf('There are no registered paths for namespace "%s".', $namespace));
+    }
+
+    foreach ($this->paths[$namespace] as $path) {
+      if (is_file($path . '/' . $shortname)) {
+        return $this->cache[$name] = $path . '/' . $shortname;
+      }
+    }
+
+    // Allow for loading based on the theme registry.
+    $hook = str_replace('.html.twig', '', strtr($name, '-', '_'));
+    $theme_registry = \Drupal::service('theme.registry')->getRuntime();
+
+    if ($theme_registry->has($hook)) {
+      $info = $theme_registry->get($hook);
+      if (isset($info['path'])) {
+        $path = $info['path'] . '/' . $name;
+      }
+      elseif (isset($info['template'])) {
+        $path = $info['template'] . '.html.twig';
+      }
+      if (isset($path) && is_file($path)) {
+        return $this->cache[$name] = $path;
+      }
+    }
+
+    throw new \Twig_Error_Loader(sprintf('Unable to find template "%s" (looked into: %s).', $name, implode(', ', $this->paths[$namespace])));
+  }
+
+}