diff --git a/core/lib/Drupal/Core/Template/Loader/StringLoader.php b/core/lib/Drupal/Core/Template/Loader/StringLoader.php
index d24b9bf..18ce9c1 100644
--- a/core/lib/Drupal/Core/Template/Loader/StringLoader.php
+++ b/core/lib/Drupal/Core/Template/Loader/StringLoader.php
@@ -25,7 +25,7 @@
  * @see \Drupal\Core\Render\Element\InlineTemplate
  * @see twig_render_template()
  */
-class StringLoader extends \Twig_Loader_String {
+class StringLoader implements \Twig_LoaderInterface, \Twig_ExistsLoaderInterface {
 
   /**
    * {@inheritdoc}
@@ -39,4 +39,25 @@ public function exists($name) {
     }
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getSource($name) {
+    return $name;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheKey($name) {
+    return $name;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function isFresh($name, $time) {
+    return true;
+  }
+
 }