diff --git a/lib/mimetypes.list.php b/lib/mimetypes.list.php
index 9135a7e3af..2aac3bbfd2 100644
--- a/lib/mimetypes.list.php
+++ b/lib/mimetypes.list.php
@@ -86,11 +86,11 @@ return array(
 	'vcf' => 'text/vcard',
 	'vcard' => 'text/vcard',
 	'doc'=>'application/msword',
-	'docx'=>'application/msword',
+	'docx'=>'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
 	'xls'=>'application/msexcel',
-	'xlsx'=>'application/msexcel',
+	'xlsx'=>'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
 	'ppt'=>'application/mspowerpoint',
-	'pptx'=>'application/mspowerpoint',
+	'pptx'=>'application/vnd.openxmlformats-officedocument.presentationml.presentation',
 	'sgf' => 'application/sgf',
 	'cdr' => 'application/coreldraw',
 	'impress' => 'text/impress',