Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 44105)
+++ src/wp-includes/functions.php	(working copy)
@@ -2654,7 +2654,7 @@
 			'3gp|3gpp'                     => 'video/3gpp', // Can also be audio
 			'3g2|3gp2'                     => 'video/3gpp2', // Can also be audio
 			// Text formats.
-			'txt|asc|c|cc|h|srt'           => 'text/plain',
+			'txt|asc|c|cc|h|srt|csv'       => 'text/plain',
 			'csv'                          => 'text/csv',
 			'tsv'                          => 'text/tab-separated-values',
 			'ics'                          => 'text/calendar',