diff --git a/core/lib/Drupal/Core/Transliteration/PhpTransliteration.php b/core/lib/Drupal/Core/Transliteration/PhpTransliteration.php
index dd4e3c2eb15a..8fbffc90e6e7 100644
--- a/core/lib/Drupal/Core/Transliteration/PhpTransliteration.php
+++ b/core/lib/Drupal/Core/Transliteration/PhpTransliteration.php
@@ -24,13 +24,12 @@ class PhpTransliteration extends BaseTransliteration {
    * Constructs a PhpTransliteration object.
    *
    * @param string $data_directory
-   *   (optional) The directory where data files reside. If omitted, defaults
-   *   to subdirectory 'data' underneath the directory where the class's PHP
-   *   file resides.
+   *   The directory where data files reside. If NULL, defaults to subdirectory
+   *   'data' underneath the directory where the class's PHP file resides.
    * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
    *   The module handler to execute the transliteration_overrides alter hook.
    */
-  public function __construct($data_directory = NULL, ModuleHandlerInterface $module_handler) {
+  public function __construct($data_directory, ModuleHandlerInterface $module_handler) {
     parent::__construct($data_directory);
 
     $this->moduleHandler = $module_handler;