diff --git a/Models/DrawImage.php b/Models/DrawImage.php
index 5c05185..03009aa 100644
--- a/Models/DrawImage.php
+++ b/Models/DrawImage.php
@@ -124,7 +124,7 @@ class DrawImage implements ArrayableInterface, \JsonSerializable
 
     public function __toString()
     {
-        return \json_encode($this->toArray());
+        return (string) \json_encode($this->toArray());
     }
 
     public function jsonSerialize()