Ember Acceptance Test Failing in PhantomJS but Passing in Chrome

I'm trying to write an acceptance test for my Ember app and I seem to be having some trouble when it comes to PhantomJS and the Ember test server.

I'm running the following versions:

Ember      : v1.13.6
Ember Data : v1.13.7

PhantomJS is failing with the following error:

Died on test #1     at http://localhost:7357/assets/test-support.js:2934
            at http://localhost:7357/assets/test-support.js:6640
            at http://localhost:7357/assets/test-loader.js:31
            at http://localhost:7357/assets/test-loader.js:21
            at http://localhost:7357/assets/test-loader.js:40
            at http://localhost:7357/assets/test-support.js:6647: Can't find variable: DS

Is this a known issue?

The test is running fine within the chrome runner.

Thanks!