diff --git a/SeedDMS_Core/Core/inc.FileUtils.php b/SeedDMS_Core/Core/inc.FileUtils.php
index b9e6e638b..058e06701 100644
--- a/SeedDMS_Core/Core/inc.FileUtils.php
+++ b/SeedDMS_Core/Core/inc.FileUtils.php
@@ -172,7 +172,7 @@ class SeedDMS_Core_File {
 
 	/**
 	 * @param $string mimetype
-	 * @return string
+	 * @return string file extension with the dot or an empty string
 	 */
 	static function fileExtension($mimetype) { /* {{{ */
 		switch($mimetype) {
@@ -267,6 +267,7 @@ class SeedDMS_Core_File {
 				'text/x-log'                                                                => 'log',
 				'audio/x-m4a'                                                               => 'm4a',
 				'application/vnd.mpegurl'                                                   => 'm4u',
+				'text/markdown'                                                             => 'md',
 				'audio/midi'                                                                => 'mid',
 				'application/vnd.mif'                                                       => 'mif',
 				'video/quicktime'                                                           => 'mov',