diff --git a/Models/NullDepartment.php b/Models/NullDepartment.php
index ebb52d1..d0b7c12 100644
--- a/Models/NullDepartment.php
+++ b/Models/NullDepartment.php
@@ -22,6 +22,6 @@ namespace Modules\Organization\Models;
  * @link    https://orange-management.org
  * @since   1.0.0
  */
-class NullDepartment extends Department
+final class NullDepartment extends Department
 {
 }
diff --git a/Models/NullPosition.php b/Models/NullPosition.php
index 7ac13f3..09f58f3 100644
--- a/Models/NullPosition.php
+++ b/Models/NullPosition.php
@@ -22,6 +22,6 @@ namespace Modules\Organization\Models;
  * @link    https://orange-management.org
  * @since   1.0.0
  */
-class NullPosition extends Position
+final class NullPosition extends Position
 {
 }
diff --git a/Models/NullUnit.php b/Models/NullUnit.php
index b2a5688..30ee574 100644
--- a/Models/NullUnit.php
+++ b/Models/NullUnit.php
@@ -22,6 +22,6 @@ namespace Modules\Organization\Models;
  * @link    https://orange-management.org
  * @since   1.0.0
  */
-class NullUnit extends Unit
+final class NullUnit extends Unit
 {
 }