diff --git a/src/ApnMessage.php b/src/ApnMessage.php
index a90fdc0..c1f8b22 100644
--- a/src/ApnMessage.php
+++ b/src/ApnMessage.php
@@ -4,6 +4,7 @@
 
 use DateTime;
 use Pushok\Client;
+use Pushok\Payload\Sound;
 
 class ApnMessage
 {
@@ -37,7 +38,7 @@ class ApnMessage
     /**
      * The sound of the notification.
      */
-    public ?string $sound = null;
+    public null|string|Sound $sound = null;
 
     /**
      * The interruption level of the notification.
@@ -199,7 +200,7 @@ public function badge(?int $badge): self
     /**
      * Set the sound of the notification.
      */
-    public function sound(?string $sound = 'default'): self
+    public function sound(null|string|Sound $sound = 'default'): self
     {
         $this->sound = $sound;