diff --git a/lisp/international/mule-conf.el b/lisp/international/mule-conf.el
index edda79ba4e..c84f0a4990 100644
--- a/lisp/international/mule-conf.el
+++ b/lisp/international/mule-conf.el
@@ -1508,6 +1508,7 @@ 'us-ascii
   :mime-charset 'us-ascii)
 
 (define-coding-system-alias 'iso-safe 'us-ascii)
+(define-coding-system-alias 'ascii 'us-ascii)
 
 (define-coding-system 'utf-7
   "UTF-7 encoding of Unicode (RFC 2152)."