diff --git a/S3.php b/S3.php
index 2078f929..0b1564b2 100644
--- a/S3.php
+++ b/S3.php
@@ -2303,11 +2303,11 @@ private function __dnsBucketName($bucket)
 	/**
 	* CURL header callback
 	*
-	* @param resource &$curl CURL resource
-	* @param string &$data Data
+	* @param resource $curl CURL resource
+	* @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')