diff --git a/src/plugin/class-engine.php b/src/plugin/class-engine.php
index 898da322..a88e6840 100644
--- a/src/plugin/class-engine.php
+++ b/src/plugin/class-engine.php
@@ -8,17 +8,22 @@ class Engine {
 
 	public function __construct() {
 		require 'enum-subject-type.php';
+		require 'class-subject.php';
+		require 'class-schema.php';
 
 		require 'class-handlers-registry.php';
-		require 'class-post-type-ui.php';
-		require 'class-transformer.php';
+		require 'class-observers-registry.php';
+
 		require 'class-subjects-controller.php';
+
 		require 'class-storage.php';
-		require 'class-schema.php';
-		require 'utils.php';
-		require 'class-subject.php';
+
+		require 'class-post-type-ui.php';
+		require 'class-transformer.php';
 		require 'class-ops.php';
 
+		require 'utils.php';
+
 		( function () {
 			new Transformer();
 			new Post_Type_UI( self::STORAGE_POST_TYPE );