diff --git a/phpBB/phpbb/mimetype/extension_guesser.php b/phpBB/phpbb/mimetype/extension_guesser.php
index 36553656e6..19de618df6 100644
--- a/phpBB/phpbb/mimetype/extension_guesser.php
+++ b/phpBB/phpbb/mimetype/extension_guesser.php
@@ -425,6 +425,7 @@ class extension_guesser extends guesser_base
 		'wb1'		=> 'application/x-qpro',
 		'wbmp'		=> 'image/vnd.wap.wbmp',
 		'web'		=> 'application/vnd.xara',
+		'webm'		=> 'audio/webm',
 		'wiz'		=> 'application/msword',
 		'wk1'		=> 'application/x-123',
 		'wmf'		=> 'windows/metafile',