Mix fails to clone from GitHub over HTTPS via 'mix deps.get'

I have successfully cloned this repository over ssh:

git clone irleif@github.com:ueberauth/ueberauth_example.git

When I try to get dependencies with mix deps.get, I get this error:

* Updating oauth (https://github.com/tim/erlang-oauth.git)
fatal: unable to access 'https://github.com/tim/erlang-oauth.git/': Couldn't connect to server

I can see that ueberauth_example is including erlang-oauth in its mix.exs, in this way:

{:oauth, github: "tim/erlang-oauth"}

The dependency doesn’t specify https or ssh, so I presume mix is defaulting to https.

However, I am able to clone the repo just fine manually over ssh, like this:

git clone irleif@github.com:tim/erlang-oauth.git

Is it somehow possible to make mix deps.get use ssh for cloning instead of https?