diff --git a/core/modules/migrate/src/Plugin/migrate/process/Callback.php b/core/modules/migrate/src/Plugin/migrate/process/Callback.php
index 0d955c7f99dfaa9ce1334a88f6d998d463d3ec31..a438189d2da4aca8d8198cb5a61b23a6720c5c7b 100644
--- a/core/modules/migrate/src/Plugin/migrate/process/Callback.php
+++ b/core/modules/migrate/src/Plugin/migrate/process/Callback.php
@@ -22,7 +22,7 @@
  * process:
  *   destination_field:
  *     plugin: callback
- *     callable: strtolower
+ *     callable: mb_strtolower
  *     source: source_field
  * @endcode
  *
@@ -34,7 +34,7 @@
  *     plugin: callback
  *     callable:
  *       - '\Drupal\Component\Utility\Unicode'
- *       - strtolower
+ *       - ucfirst
  *     source: source_field
  * @endcode
  *