Index: wp-includes/class-http.php
===================================================================
--- wp-includes/class-http.php	(revision 20171)
+++ wp-includes/class-http.php	(working copy)
@@ -1327,6 +1327,7 @@
 	 * hosts that won't be sent through the proxy.
 	 *
 	 * @uses WP_PROXY_BYPASS_HOSTS
+	 * @uses WP_PROXY_LOCAL_HOSTS
 	 * @since 2.8.0
 	 *
 	 * @param string $uri URI to check.
@@ -1344,7 +1345,7 @@
 		$home = parse_url( get_option('siteurl') );
 
 		if ( $check['host'] == 'localhost' || $check['host'] == $home['host'] )
-			return false;
+			return WP_PROXY_LOCAL_HOSTS;
 
 		if ( !defined('WP_PROXY_BYPASS_HOSTS') )
 			return true;
Index: wp-includes/default-constants.php
===================================================================
--- wp-includes/default-constants.php	(revision 20171)
+++ wp-includes/default-constants.php	(working copy)
@@ -69,6 +69,9 @@
 
 	if ( !defined('SHORTINIT') )
 		define('SHORTINIT', false);
+
+	if ( !defined('WP_PROXY_LOCAL_HOSTS') )
+		define('WP_PROXY_LOCAL_HOSTS', false);
 }
 
 /**