diff --git a/src/Controllers/AwsSnsController.php b/src/Controllers/AwsSnsController.php
index e01cddc..9561d0c 100644
--- a/src/Controllers/AwsSnsController.php
+++ b/src/Controllers/AwsSnsController.php
@@ -16,7 +16,7 @@ public function __invoke()
         $message = Message::fromRawPostData();
 
         $validator = new MessageValidator(function ($certUrl) {
-            return Cache::rememberForever($certUrl, function ($certUrl) {
+            return Cache::rememberForever($certUrl, function () use ($certUrl) {
                 return file_get_contents($certUrl);
             });
         });