Rails - Error loading gem through git

I've created a Rails Engine and I've only used it in an Rails application by including it in the Gemfile with a local source path as follows:

gem 'engine_name', path: 'path/to/engine'

After placing the engine on git and changing the Gemfile line to the following:

gem 'engine_name', git: 'ssh_address', branch: 'branch_name'

I get the following error:

(...)/.rvm/gems/ruby-2.1.3/gems/bundler-1.12.5/lib/bundler/runtime.rb:89:in `rescue in block (2 levels) in require': 
There was an error while trying to load the gem 'engine_name'. (Bundler::GemRequireError)
Gem Load Error is: uninitialized constant EngineName

(Sorry for not specifying any names in particular) I have another engine I've created included in the same way with no problems but I can't figure out what the problem is here.