diff --git a/Models/Event.php b/Models/Event.php
index 3bd6e20..9816f7e 100755
--- a/Models/Event.php
+++ b/Models/Event.php
@@ -440,7 +440,7 @@ class Event
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/EventAttribute.php b/Models/EventAttribute.php
index 006081a..1c864ea 100755
--- a/Models/EventAttribute.php
+++ b/Models/EventAttribute.php
@@ -97,7 +97,7 @@ class EventAttribute implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/EventAttributeType.php b/Models/EventAttributeType.php
index b3ab8ae..17b6574 100755
--- a/Models/EventAttributeType.php
+++ b/Models/EventAttributeType.php
@@ -165,7 +165,7 @@ class EventAttributeType implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/EventAttributeTypeL11n.php b/Models/EventAttributeTypeL11n.php
index e6b2fce..96437a1 100755
--- a/Models/EventAttributeTypeL11n.php
+++ b/Models/EventAttributeTypeL11n.php
@@ -129,7 +129,7 @@ class EventAttributeTypeL11n implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }
diff --git a/Models/EventAttributeValue.php b/Models/EventAttributeValue.php
index f690fba..d3f8445 100755
--- a/Models/EventAttributeValue.php
+++ b/Models/EventAttributeValue.php
@@ -248,7 +248,7 @@ class EventAttributeValue implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }