diff --git a/src/Config/ConfigReadonlyStorage.php b/src/Config/ConfigReadonlyStorage.php
index 43934f5..eebba14 100644
--- a/src/Config/ConfigReadonlyStorage.php
+++ b/src/Config/ConfigReadonlyStorage.php
@@ -23,13 +23,6 @@ class ConfigReadonlyStorage extends CachedStorage {
   use ConfigReadonlyWhitelistTrait;
 
   /**
-   * The module handler.
-   *
-   * @var \Drupal\Core\Extension\ModuleHandlerInterface
-   */
-  protected $moduleHandler;
-
-  /**
    * The used lock backend instance.
    *
    * @var \Drupal\Core\Lock\LockBackendInterface
@@ -61,7 +54,7 @@ class ConfigReadonlyStorage extends CachedStorage {
     parent::__construct($storage, $cache);
     $this->lock = $lock;
     $this->requestStack = $request_stack;
-    $this->moduleHandler = $module_handler;
+    $this->setModuleHandler($module_handler);
   }
 
   /**
diff --git a/src/ConfigReadonlyWhitelistTrait.php b/src/ConfigReadonlyWhitelistTrait.php
index 6f6151a..1121f50 100644
--- a/src/ConfigReadonlyWhitelistTrait.php
+++ b/src/ConfigReadonlyWhitelistTrait.php
@@ -17,6 +17,23 @@ trait ConfigReadonlyWhitelistTrait {
   protected $patterns = [];
 
   /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
+   * Sets the module handler.
+   *
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler.
+   */
+  public function setModuleHandler(ModuleHandlerInterface $module_handler) {
+    $this->moduleHandler = $module_handler;
+  }
+
+  /**
    * Get whitelist patterns.
    *
    * @return string[]
diff --git a/src/EventSubscriber/ReadOnlyFormSubscriber.php b/src/EventSubscriber/ReadOnlyFormSubscriber.php
index 300e9d6..3924e13 100644
--- a/src/EventSubscriber/ReadOnlyFormSubscriber.php
+++ b/src/EventSubscriber/ReadOnlyFormSubscriber.php
@@ -18,20 +18,13 @@ class ReadOnlyFormSubscriber implements EventSubscriberInterface {
   use ConfigReadonlyWhitelistTrait;
 
   /**
-   * The module handler.
-   *
-   * @var \Drupal\Core\Extension\ModuleHandlerInterface
-   */
-  protected $moduleHandler;
-
-  /**
    * ReadOnlyFormSubscriber constructor.
    *
    * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
    *   The module handler to invoke hooks.
    */
   public function __construct(ModuleHandlerInterface $module_handler) {
-    $this->moduleHandler = $module_handler;
+    $this->setModuleHandler($module_handler);
   }
 
   /**