Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 23294)
+++ wp-includes/formatting.php	(working copy)
@@ -831,6 +831,7 @@
 	$filename = str_replace($special_chars, '', $filename);
 	$filename = preg_replace('/[\s-]+/', '-', $filename);
 	$filename = trim($filename, '.-_');
+	$filename = remove_accents($filename);
 
 	// Split the filename into a base and extension[s]
 	$parts = explode('.', $filename);