diff --git a/src/calibre/__init__.py b/src/calibre/__init__.py
index ff4bab6a9a..48f2c0ecec 100644
--- a/src/calibre/__init__.py
+++ b/src/calibre/__init__.py
@@ -41,6 +41,8 @@ mimetypes.add_type('application/vnd.palm',                '.pdb')
 mimetypes.add_type('application/x-mobipocket-ebook',      '.mobi')
 mimetypes.add_type('application/x-mobipocket-ebook',      '.prc')
 mimetypes.add_type('application/x-mobipocket-ebook',      '.azw')
+mimetypes.add_type('application/x-cbz',                   '.cbz')
+mimetypes.add_type('application/x-cbr',                   '.cbr')
 mimetypes.add_type('image/wmf',                           '.wmf')
 guess_type = mimetypes.guess_type
 import cssutils