diff -r deb3e5857d8c Doc/library/codecs.rst
--- a/Doc/library/codecs.rst	Thu Oct 27 19:30:10 2016 +0900
+++ b/Doc/library/codecs.rst	Thu Oct 27 22:07:32 2016 +0800
@@ -978,9 +978,9 @@
    Some common encodings can bypass the codecs lookup machinery to
    improve performance.  These optimization opportunities are only
    recognized by CPython for a limited set of aliases: utf-8, utf8,
-   latin-1, latin1, iso-8859-1, mbcs (Windows only), ascii, utf-16,
-   and utf-32.  Using alternative spellings for these encodings may
-   result in slower execution.
+   latin-1, latin1, iso-8859-1, iso8859-1, mbcs (Windows only), ascii,
+   us-ascii, utf-16, utf16, utf-32 and utf32.  Using alternative
+   spellings for these encodings may result in slower execution.
 
 Many of the character sets support the same languages. They vary in individual
 characters (e.g. whether the EURO SIGN is supported or not), and in the