diff --git a/system/helpers/url_helper.php b/system/helpers/url_helper.php
index 3621963..e82a51d 100644
--- a/system/helpers/url_helper.php
+++ b/system/helpers/url_helper.php
@@ -50,7 +50,7 @@
 	 * @param	string	$protocol
 	 * @return	string
 	 */
-	function site_url($uri = '')
+	function site_url($uri = '', $protocol = NULL)
 	{
 		$site_url = get_instance()->config->site_url($uri);