diff --git a/Models/Promotion.php b/Models/Promotion.php
index 02c5ce0..e1b670e 100755
--- a/Models/Promotion.php
+++ b/Models/Promotion.php
@@ -400,7 +400,7 @@ class Promotion
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/PromotionAttribute.php b/Models/PromotionAttribute.php
index b15e51a..99e0e6d 100755
--- a/Models/PromotionAttribute.php
+++ b/Models/PromotionAttribute.php
@@ -97,7 +97,7 @@ class PromotionAttribute implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/PromotionAttributeType.php b/Models/PromotionAttributeType.php
index f886684..0876fb6 100755
--- a/Models/PromotionAttributeType.php
+++ b/Models/PromotionAttributeType.php
@@ -165,7 +165,7 @@ class PromotionAttributeType implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/PromotionAttributeTypeL11n.php b/Models/PromotionAttributeTypeL11n.php
index 30b054d..34513c7 100755
--- a/Models/PromotionAttributeTypeL11n.php
+++ b/Models/PromotionAttributeTypeL11n.php
@@ -129,7 +129,7 @@ class PromotionAttributeTypeL11n implements \JsonSerializable, ArrayableInterfac
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/PromotionAttributeValue.php b/Models/PromotionAttributeValue.php
index 70c899e..61244d9 100755
--- a/Models/PromotionAttributeValue.php
+++ b/Models/PromotionAttributeValue.php
@@ -248,7 +248,7 @@ class PromotionAttributeValue implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }