diff --git a/Models/NullAccount.php b/Models/NullAccount.php
index fee3f6c..e90e5bc 100755
--- a/Models/NullAccount.php
+++ b/Models/NullAccount.php
@@ -36,4 +36,12 @@ final class NullAccount extends Account
         parent::__construct();
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullAccountPermission.php b/Models/NullAccountPermission.php
index 785b922..296b17e 100755
--- a/Models/NullAccountPermission.php
+++ b/Models/NullAccountPermission.php
@@ -36,4 +36,12 @@ final class NullAccountPermission extends AccountPermission
         $this->id = $id;
         parent::__construct();
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullAddress.php b/Models/NullAddress.php
index cd95226..01ab4da 100755
--- a/Models/NullAddress.php
+++ b/Models/NullAddress.php
@@ -35,4 +35,12 @@ final class NullAddress extends Address
     {
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullGroup.php b/Models/NullGroup.php
index bb6c77d..5439f2a 100755
--- a/Models/NullGroup.php
+++ b/Models/NullGroup.php
@@ -36,4 +36,12 @@ final class NullGroup extends Group
         $this->id = $id;
         parent::__construct();
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullGroupPermission.php b/Models/NullGroupPermission.php
index ba0d02f..d591440 100755
--- a/Models/NullGroupPermission.php
+++ b/Models/NullGroupPermission.php
@@ -36,4 +36,12 @@ final class NullGroupPermission extends GroupPermission
         $this->id = $id;
         parent::__construct();
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullModule.php b/Models/NullModule.php
index 602c1d2..b1d24c0 100755
--- a/Models/NullModule.php
+++ b/Models/NullModule.php
@@ -36,4 +36,12 @@ final class NullModule extends Module
         parent::__construct();
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }