diff --git a/Models/Item.php b/Models/Item.php
index a8aede2..2bff949 100755
--- a/Models/Item.php
+++ b/Models/Item.php
@@ -332,7 +332,7 @@ class Item
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/ItemAttribute.php b/Models/ItemAttribute.php
index 8139982..365581f 100755
--- a/Models/ItemAttribute.php
+++ b/Models/ItemAttribute.php
@@ -97,7 +97,7 @@ class ItemAttribute implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/ItemAttributeType.php b/Models/ItemAttributeType.php
index a0a2d04..992b754 100755
--- a/Models/ItemAttributeType.php
+++ b/Models/ItemAttributeType.php
@@ -165,7 +165,7 @@ class ItemAttributeType implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/ItemAttributeTypeL11n.php b/Models/ItemAttributeTypeL11n.php
index 9f82ed8..27f586f 100755
--- a/Models/ItemAttributeTypeL11n.php
+++ b/Models/ItemAttributeTypeL11n.php
@@ -129,7 +129,7 @@ class ItemAttributeTypeL11n implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/ItemAttributeValue.php b/Models/ItemAttributeValue.php
index b6ad6a1..6a00169 100755
--- a/Models/ItemAttributeValue.php
+++ b/Models/ItemAttributeValue.php
@@ -248,7 +248,7 @@ class ItemAttributeValue implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/ItemL11n.php b/Models/ItemL11n.php
index bd5daa5..b290f0c 100755
--- a/Models/ItemL11n.php
+++ b/Models/ItemL11n.php
@@ -137,7 +137,7 @@ class ItemL11n implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/ItemL11nType.php b/Models/ItemL11nType.php
index 5f9c459..f9f0828 100755
--- a/Models/ItemL11nType.php
+++ b/Models/ItemL11nType.php
@@ -80,7 +80,7 @@ class ItemL11nType implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }