diff --git a/core/lib/Drupal/Core/Extension/module.api.php b/core/lib/Drupal/Core/Extension/module.api.php
index f4cade9..4ce18d0 100644
--- a/core/lib/Drupal/Core/Extension/module.api.php
+++ b/core/lib/Drupal/Core/Extension/module.api.php
@@ -32,6 +32,9 @@
  * - Configuration schema changes: adding/removing/renaming a config key,
  *   changing the expected data type or value structure, changing dependencies,
  *   etc.
+ * - Configuration changes: sometimes even though the configuration schema
+ *   does not change, you may still need to update configuration to be
+ *   compatible with new code.
  * - Database schema changes: adding, changing, or removing a database table or
  *   field; moving stored data to different fields or tables; changing the
  *   format of stored data.
@@ -519,13 +522,18 @@ function hook_install_tasks_alter(&$tasks, $install_state) {
  *
  * Because of these reasons, you'll need to use care in writing your update
  * function. Some things to think about:
- * - Never assume that the database or configuration schema is the same when
- *   the update will run as it is when you wrote the update function. So,
- *   when saving configuration, use the $has_trusted_data = TRUE parameter so
- *   that schema is ignored, and when updating a database table or field, put
- *   the schema information you want to update to directly into your function
- *   instead of calling your hook_schema() function to retrieve it (this is
- *   one case where the right thing to do is copy and paste the code).
+ * - Never assume that the database schema is the same when the update will run
+ *   as it is when you wrote the update function. So, when updating a database
+ *   table or field, put the schema information you want to update to directly
+ *   into your function instead of calling your hook_schema() function to
+ *   retrieve it (this is one case where the right thing to do is copy and paste
+ *   the code).
+ * - Never assume that the configuration schema is the same when the update will
+ *   run as it is when you wrote the update function. So, when saving
+ *   configuration, use the $has_trusted_data = TRUE parameter so that schema is
+ *   ignored, and make sure that the configuration data you are saving matches
+ *   the configuration schema at the time when you write the update function
+ *   (later updates may change it again to match new schema changes).
  * - Be careful about API functions and especially CRUD operations that you use
  *   in your update function. If they invoke hooks or use services, they may
  *   not behave as expected, and it may actually not be appropriate to use the