diff --git a/Models/Media.php b/Models/Media.php
index eaa23bc..ab54416 100755
--- a/Models/Media.php
+++ b/Models/Media.php
@@ -449,7 +449,7 @@ class Media implements \JsonSerializable
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/MediaContent.php b/Models/MediaContent.php
index 3102205..e914b9a 100644
--- a/Models/MediaContent.php
+++ b/Models/MediaContent.php
@@ -63,7 +63,7 @@ class MediaContent implements \JsonSerializable
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/MediaType.php b/Models/MediaType.php
index 8b1163d..1db6fc7 100644
--- a/Models/MediaType.php
+++ b/Models/MediaType.php
@@ -133,7 +133,7 @@ class MediaType implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/MediaTypeL11n.php b/Models/MediaTypeL11n.php
index 84a00a5..3e9fa94 100644
--- a/Models/MediaTypeL11n.php
+++ b/Models/MediaTypeL11n.php
@@ -126,7 +126,7 @@ class MediaTypeL11n implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }