--- a/contrib/mercurial.el
+++ b/contrib/mercurial.el
@@ -521,7 +521,7 @@ directory names from the file system. W
(completing-read (format "Revision%s (%s): "
(or prompt "")
(or default "tip"))
- (map 'list 'cons revs revs)
+ (mapcar (lambda (x) (cons x x)) revs)
nil
nil
nil