automake fails when using add-missing option

automake --add-missing --copy does not create or copy any missing files.
I `apt purge autoconf` then `apt install autoconf` in case the Gnu required files had gone missing from my system for any reason.
The work-around is easy of course, just `touch README` etc.

>> lsb_release -rd
Description: Ubuntu 16.04.4 LTS
Release: 16.04

>> apt-cache policy autoconf
autoconf:
  Installed: 2.69-9
  Candidate: 2.69-9
  Version table:
 *** 2.69-9 500
        500 http://th.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
        500 http://th.archive.ubuntu.com/ubuntu xenial/main i386 Packages
        100 /var/lib/dpkg/status

>> automake --add-missing --copy
I expected it add a missing README file

This happened instead.
Makefile.am: error: required file './README' not found