diff --git a/lib/SendGrid/Email.php b/lib/SendGrid/Email.php
index <HASH>..<HASH> 100644
--- a/lib/SendGrid/Email.php
+++ b/lib/SendGrid/Email.php
@@ -353,7 +353,7 @@ class Email {
         }

 

         $contents   = '@' . $file; 

-        if (class_exists('CurlFile')) { // php >= 5.5

+        if (class_exists('CurlFile', false)) { // php >= 5.5

           $contents = new \CurlFile($file, $extension, $filename);

         }
Do not call autoloader when checking if CurlFile class exists

As CurlFile is a built-in class there is no reason to invoke the autoloader.