diff --git a/lib/Cake/Network/CakeResponse.php b/lib/Cake/Network/CakeResponse.php
index 7f8ea45070e..79be981acb0 100644
--- a/lib/Cake/Network/CakeResponse.php
+++ b/lib/Cake/Network/CakeResponse.php
@@ -98,6 +98,7 @@ class CakeResponse {
 		'dir' => 'application/x-director',
 		'dms' => 'application/octet-stream',
 		'doc' => 'application/msword',
+		'docx' => 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
 		'drw' => 'application/drafting',
 		'dvi' => 'application/x-dvi',
 		'dwg' => 'application/acad',
@@ -134,6 +135,7 @@ class CakeResponse {
 		'pot' => 'application/vnd.ms-powerpoint',
 		'pps' => 'application/vnd.ms-powerpoint',
 		'ppt' => 'application/vnd.ms-powerpoint',
+		'pptx' => 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
 		'ppz' => 'application/vnd.ms-powerpoint',
 		'pre' => 'application/x-freelance',
 		'prt' => 'application/pro_eng',
@@ -178,6 +180,7 @@ class CakeResponse {
 		'xll' => 'application/vnd.ms-excel',
 		'xlm' => 'application/vnd.ms-excel',
 		'xls' => 'application/vnd.ms-excel',
+		'xlsx' => 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
 		'xlw' => 'application/vnd.ms-excel',
 		'zip' => 'application/zip',
 		'aif' => 'audio/x-aiff',