diff --git a/Models/NullSupplier.php b/Models/NullSupplier.php
index 5e1a93b..b4b3455 100755
--- a/Models/NullSupplier.php
+++ b/Models/NullSupplier.php
@@ -36,4 +36,12 @@ final class NullSupplier extends Supplier
         $this->id = $id;
         parent::__construct();
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullSupplierAttribute.php b/Models/NullSupplierAttribute.php
index 36f1c84..fe4eefd 100755
--- a/Models/NullSupplierAttribute.php
+++ b/Models/NullSupplierAttribute.php
@@ -36,4 +36,12 @@ final class NullSupplierAttribute extends SupplierAttribute
         parent::__construct();
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullSupplierAttributeType.php b/Models/NullSupplierAttributeType.php
index 453cac3..1333f86 100755
--- a/Models/NullSupplierAttributeType.php
+++ b/Models/NullSupplierAttributeType.php
@@ -35,4 +35,12 @@ final class NullSupplierAttributeType extends SupplierAttributeType
     {
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullSupplierAttributeTypeL11n.php b/Models/NullSupplierAttributeTypeL11n.php
index 95589bc..ea9ad95 100755
--- a/Models/NullSupplierAttributeTypeL11n.php
+++ b/Models/NullSupplierAttributeTypeL11n.php
@@ -35,4 +35,12 @@ final class NullSupplierAttributeTypeL11n extends SupplierAttributeTypeL11n
     {
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }
diff --git a/Models/NullSupplierAttributeValue.php b/Models/NullSupplierAttributeValue.php
index 7dc49aa..1807dd5 100755
--- a/Models/NullSupplierAttributeValue.php
+++ b/Models/NullSupplierAttributeValue.php
@@ -35,4 +35,12 @@ final class NullSupplierAttributeValue extends SupplierAttributeValue
     {
         $this->id = $id;
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function jsonSerialize() : mixed
+    {
+        return ['id' => $this->id];
+    }
 }