Removing newest duplicates created during the import process

[codeinabox]

As I forgot to disable copying on import, my collection now has a lot of duplicate files where a new file was copied over that uses a different naming scheme to the existing files. I am trying to use Beets to detect and remove these new copies based on modified time using this config:

duplicates:
    tiebreak:
        items: [mtime]

When I run beets dup -p the files it lists are the original oldest ones. How do I do a tie-break, treating the newest file as the duplicates?

[codeinabox]

Simply put, is there a way to inverse the tie-break condition?