diff --git a/core/lib/Drupal/Core/Render/theme.api.php b/core/lib/Drupal/Core/Render/theme.api.php
index 496d799ca0b02188d3a82e23581471c8a4b8e108..f59c4213ae6402d1ae21f5120b984de32cea3adb 100644
--- a/core/lib/Drupal/Core/Render/theme.api.php
+++ b/core/lib/Drupal/Core/Render/theme.api.php
@@ -685,6 +685,7 @@ function hook_theme_suggestions_HOOK(array $variables) {
  *
  * In the following example, we provide an alternative template suggestion to
  * node and taxonomy term templates based on the user being logged in.
+ *
  * @code
  * function MYMODULE_theme_suggestions_alter(array &$suggestions, array $variables, $hook) {
  *   if (\Drupal::currentUser()->isAuthenticated() && in_array($hook, array('node', 'taxonomy_term'))) {
@@ -694,8 +695,9 @@ function hook_theme_suggestions_HOOK(array $variables) {
  *
  * @endcode
  *
- * @param array $suggestions
- *   An array of alternate, more specific names for template files.
+ * @param array &$suggestions
+ *   An array of alternate, more specific names for template files, passed by
+ *   reference.
  * @param array $variables
  *   An array of variables passed to the theme hook. Note that this hook is
  *   invoked before any variable preprocessing.