debian stretch sources.list unable to find i386 packages.

apt-get update:
E: Failed to fetch
ftp://ftp.mondorescue.org/test/debian/dists/9/InRelease  Unable to
find expected entry 'contrib/binary-i386/Packages' in Release file
(Wrong sources.list entry or malformed file)
E: Some index files failed to download. They have been ignored, or old
ones used instead.

Based on:
ftp://ftp.mondorescue.org/test/debian/9/mondorescue-test.sources.list

Perhaps [arch=amd64] should be added (in the mean time?), to make:
$ cat mondorescue-test.sources.list
deb [arch=amd64] ftp://ftp.mondorescue.org/test/debian 9 contrib
deb-src [arch=amd64] ftp://ftp.mondorescue.org/test/debian 9 contrib

Solving the issue, for the moment.