diff --git a/src/Fcm.php b/src/Fcm.php
index 845716a..f315c9d 100644
--- a/src/Fcm.php
+++ b/src/Fcm.php
@@ -77,7 +77,7 @@ public function send()
     {
         $payloads = [
             'content_available' => true,
-            'priority' => $this->priority ?? 'high',
+            'priority' => isset($this->priority) ? $this->priority : 'high',
             'data' => $this->data,
             'notification' => $this->notification
         ];