diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index 3b7dbf4..9bbe970 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -1250,7 +1250,7 @@ function hook_template_preprocess_default_variables_alter(&$variables) {
  *   The file extension the theme engine will recognize.
  */
 function hook_extension() {
-  // Extension for template base names in Twig
+  // Extension for template base names in Twig.
   return '.html.twig';
 }
 
@@ -1261,15 +1261,15 @@ function hook_extension() {
  * ENGINE_render_template(). It gets passed a template name and an array of
  * variables and returns a string containing the rendered template.
  *
- * @param string template_file
+ * @param string $template_file
  *   The relative path to the template to be rendered including its extension in
  *   the format 'path/to/TEMPLATE_NAME.EXT'. The path should be relative to the
- *   drupal root directory.
+ *   Drupal root directory.
  * @param array $variables
  *   A keyed array of variables that are available for composing the output. The
  *   theme engine is responsible for passing all the variables to the template.
- *   If all or just a subset of those variables are used in the template may
- *   vary depending on the code in the template.
+ *   Depending on the code in the template, all or just a subset of those
+ *   variables might be used in the template.
  *
  * @return string
  *   The output generated from the template. In most cases this will be a string
diff --git a/core/themes/engines/twig/twig.engine b/core/themes/engines/twig/twig.engine
index 2ffe88f..bb26ae1 100644
--- a/core/themes/engines/twig/twig.engine
+++ b/core/themes/engines/twig/twig.engine
@@ -20,9 +20,6 @@ function twig_theme($existing, $type, $theme, $path) {
 
 /**
  * Implements hook_extension().
- *
- * @return string
- *  The file extension the Twig theme engine will recognize
  */
 function twig_extension() {
   return '.html.twig';