diff -u b/core/lib/Drupal/Core/Template/TwigExtension.php b/core/lib/Drupal/Core/Template/TwigExtension.php
--- b/core/lib/Drupal/Core/Template/TwigExtension.php
+++ b/core/lib/Drupal/Core/Template/TwigExtension.php
@@ -77,7 +77,7 @@
       new \Twig_SimpleFunction('path', array($this, 'getPath'), array('is_safe_callback' => array($this, 'isUrlGenerationSafe'))),
       new \Twig_SimpleFunction('url_from_path', array($this, 'getUrlFromPath'), array('is_safe_callback' => array($this, 'isUrlGenerationSafe'))),
       new \Twig_SimpleFunction('link', array($this, 'getLink')),
-      new \Twig_SimpleFunction('addLib', array($this, 'addLibraries')),
+      new \Twig_SimpleFunction('add_libraries', array($this, 'addLibraries')),
     );
   }