Setting the expires_at parameter on a download_archive_url doesn't seem to do anything

I'm trying to override the default expiration timestamp on a download_archive_url when creating an archive using the Cloudinary::Utils.download_archive_url(options = {}) call. I see in the documentation the expires_at parameter is described as follows:

The date (UNIX time in seconds) for the URL expiration (e.g., 1415060076). Only relevant when using the 'download' SDK methods and the 'download' mode in direct calls. Default: 1 hour from the current time.

I set the mode to download in my options and included :expires_at => (Time.now + 24.hours).to_i in the options, but when I run the download command and generate the download url to pass along to my Mailer there isn't an expires_at parameter present in the url.

Has anyone had success setting the expires_at parameter in either the Cloudinary::Utils.download_archive_url or the Cloudinary::Uploader.create_archive API calls?