diff --git a/core/lib/Drupal/Core/Extension/module.api.php b/core/lib/Drupal/Core/Extension/module.api.php
index f06ca69..7acc0fd 100644
--- a/core/lib/Drupal/Core/Extension/module.api.php
+++ b/core/lib/Drupal/Core/Extension/module.api.php
@@ -477,13 +477,13 @@ function hook_install_tasks_alter(&$tasks, $install_state) {
  * - Cache invalidation.
  * - Using \Drupal::configFactory()->getEditable() and \Drupal::config().
  *   Implementations must:
- *   - not make any assumption that the config data is valid.
- *   - use be the correct data type when changing configuration values as
- *     specified by its configuration schema at the time the update hook is
- *     written. If the data type changes in a subsequent code change, a
- *     subsequent update hook is responsible for ensuring the final data type
- *     aligns with the configuration schema.
- *   - use the $has_trusted_data argument for \Drupal\Core\Config\Config::save()
+ *   - Not make any assumption that the config data is valid.
+ *   - Use the correct data type when changing configuration values as specified
+ *     by its configuration schema at the time the update hook is written. If
+ *     the data type changes in a subsequent code change, a subsequent update
+ *     hook is responsible for ensuring the final data type aligns with the
+ *     configuration schema.
+ *   - Use the $has_trusted_data argument for \Drupal\Core\Config\Config::save()
  *     so that configuration schemas are not used whilst saving configuration.
  * - Marking a container for rebuild.
  *
diff --git a/core/modules/language/src/EventSubscriber/ConfigSubscriber.php b/core/modules/language/src/EventSubscriber/ConfigSubscriber.php
index 3469949..e1875ce 100644
--- a/core/modules/language/src/EventSubscriber/ConfigSubscriber.php
+++ b/core/modules/language/src/EventSubscriber/ConfigSubscriber.php
@@ -61,8 +61,8 @@ public function __construct(LanguageManagerInterface $language_manager, Language
   /**
    * Causes the container to be rebuilt on the next request.
    *
-   * This event assumes that the new default langcode and old default langcode
-   * are valid langcodes. If the schema definition of either
+   * This event subscriber assumes that the new default langcode and old default
+   * langcode are valid langcodes. If the schema definition of either
    * system.site:default_langcode or language.negotiation::url.prefixes changes
    * then this event must be changed to work with both the old and new schema
    * definition so this event is update safe.
@@ -81,7 +81,8 @@ public function onConfigSave(ConfigCrudEvent $event) {
         $this->languageManager->reset();
 
         // Directly update language negotiation settings instead of calling
-        // language_negotiation_url_prefixes_update().
+        // language_negotiation_url_prefixes_update() to ensure that the code
+        // obeys the hook_update_N() restrictions.
         $negotiation_config = $this->configFactory->getEditable('language.negotiation');
         $negotiation_changed = FALSE;
         $url_prefixes = $negotiation_config->get('url.prefixes');