Error installing ember-cli-mocha

I'm trying to setup an EmberJS project using ember-cli. I want to be able to use Mocha/Chai instead of the default qunit, but I am getting an error at the first step on installing ember-cli-mocha.

I create the new ember project with ember new my-project and then from within the project folder I run ember install ember-cli-mocha, selecting Yes to overwrite the tests/test-helper.js.

In the output, immediately following the Installed browser packages via Bower. message I see:

Package ember-cli/ember-cli-test-loader=ember-cli/ember-cli-test-loader not found

I can't find any information on this directly. I've tried installing the various packages themselves, before the ember-cli-mocha package via npm and bower, but I always get that message when installing ember-cli-mocha through ember-cli.

Anyone else have experience with this? Thanks in advance!