Autoload generation fails with emacs 21

Doing an installation of vm 8.1.1 on an emacs 21 system, the build failed when creating vm-autoloads.el. I believe I tracked this down to the end of the vm-build.el file, where this code is found:

      (if (>= emacs-major-version 22)
          (update-autoloads-from-directories source-dir)
 (if (>= emacs-major-version 21)
            (update-directory-autoloads source-dir)
          (error "Do not know how to generate autoloads"))))))

That is, for emacs 22 and later, update-autoloads-from-directories is used. For emacs 21, update-directory-autoloads is used. But that seems to be the wrong way around. In emacs 21 I have update-autoloads-from-directories available but not update-directory-autoloads. And looking at the documentation of update-directory-autoloads in emacs 23 it says

    update-autoloads-from-directories is an alias for
    `update-directory-autoloads'.

    (update-autoloads-from-directories &rest DIRS)

    This function is obsolete since 22.1;
    use `update-directory-autoloads' instead.

So it does seem like the branches in the test are the wrong way around.