Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 7043)
+++ wp-includes/functions.php	(working copy)
@@ -1188,12 +1188,12 @@
 		'asf|asx|wax|wmv|wmx' => 'video/asf',
 		'avi' => 'video/avi',
 		'mov|qt' => 'video/quicktime',
-		'mpeg|mpg|mpe' => 'video/mpeg',
+		'mpeg|mpg|mpe|mp4' => 'video/mpeg',
 		'txt|c|cc|h' => 'text/plain',
 		'rtx' => 'text/richtext',
 		'css' => 'text/css',
 		'htm|html' => 'text/html',
-		'mp3|mp4' => 'audio/mpeg',
+		'mp3|m4a' => 'audio/mpeg',
 		'ra|ram' => 'audio/x-realaudio',
 		'wav' => 'audio/wav',
 		'ogg' => 'audio/ogg',