Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 12541)
+++ wp-includes/pluggable.php	(working copy)
@@ -858,6 +858,10 @@
 	if ( !$location ) // allows the wp_redirect filter to cancel a redirect
 		return false;
 
+	require_once('idna_convert.class.php');
+	$IDN = new idna_convert();
+	$location = $IDN->encode($location);
+
 	$location = wp_sanitize_redirect($location);
 
 	if ( $is_IIS ) {