Since I had the repository installed via the instructions here, and I had updated, my system had the older version cached. To see which versions are available for you to install, you can use:
sudo aptitude versions enpass
And then, install the exact version you need using the command in my first post.
If you don't have aptitude installed, you may be able to do the same with apt-get instead. I like aptitude for reasons that are divergent from this thread, and have not tested other methods, so I cannot speak for them.