diff --git a/Models/DrawImage.php b/Models/DrawImage.php
index aef0591..0a906df 100755
--- a/Models/DrawImage.php
+++ b/Models/DrawImage.php
@@ -69,7 +69,7 @@ class DrawImage implements \JsonSerializable, ArrayableInterface
     /**
      * {@inheritdoc}
      */
-    public function jsonSerialize()
+    public function jsonSerialize() : mixed
     {
         return $this->toArray();
     }