diff --git a/S3.php b/S3.php
index 2078f929..55603bbb 100644
--- a/S3.php
+++ b/S3.php
@@ -2307,7 +2307,7 @@ private function __dnsBucketName($bucket)
 	* @param string &$data Data
 	* @return integer
 	*/
-	private function __responseHeaderCallback(&$curl, &$data)
+	private function __responseHeaderCallback($curl, $data)
 	{
 		if (($strlen = strlen($data)) <= 2) return $strlen;
 		if (substr($data, 0, 4) == 'HTTP')