How do I upgrade docker on my Ubuntu 14.04 machine?

I tried following the instructions to upgrade Docker on my local machine provided on their website. However, when I do that it ends up just downloading a vanilla HTML file:

$ wget -N https://get.docker.com/ | sh
--2015-05-05 15:13:03--  https://get.docker.com/
Resolving get.docker.com (get.docker.com)... 162.242.195.82
Connecting to get.docker.com (get.docker.com)|162.242.195.82|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 7452 (7.3K) [text/plain]
Saving to: ‘index.html’

100%[=============================>] 7,452       --.-K/s   in 0s      

2015-05-05 15:13:03 (677 MB/s) - ‘index.html’ saved [7452/7452]

This is obviously not what I want.