Pretender and QUnit: Error: Assertion Failed: The response from a findQuery must be an Array, not undefined

A recent update seems to have broken my tests. I'm using Pretender to mock server calls, and I'm getting the error Error: Assertion Failed: The response from a findQuery must be an Array, not undefined.

Note that I don't get errors when I visit that page in my app. This error only appears when I run the test.

I've already looked at this, this, and this, but none of those solutions seem to apply in my case.

Here's the relevant code in my Pretender helper:

var scores = [
  {
    id: 1,
    name: 'score 1'
  }
];

var levels = [
  {
    id: 1,
    name: 'level 1',
    score_id: 1
  }, {
    id: 2,
    name: 'level 2',
    score_id: 1
  }, {
    id: 3,
    name: 'level 3',
    score_id: 1
  }
];

return new Pretender(function() {
  this.get('api/v1/scores/:id', function(request) {
    var score = scores.find(function(score) {
      // in the failing test, request.params.id is '1'
      if (score.id === parseInt(request.params.id, 10)) {
        return score;
      }
    });

    return [200, {"Content-Type": "application/json"}, JSON.stringify({
      score: score,
      levels: levels
    })];
  });
});

And this is the test:

test('displays "Project Score"', function() {
  visit('/projects/32/scores/1');

  andThen(function() {
    equal(find('h3.title').text(), 'Project Score');
  });
});

Note that this only affects tests using show routes like the one above. Tests that use this route work normally:

this.get('api/v1/scores', function(request) {
  return [200, {"Content-Type": "application/json"}, JSON.stringify({
    scores: scores
  })];
});

I tried bypassing the find by doing this:

this.get('api/v1/scores/:id', function(request) {
  return [200, {"Content-Type": "application/json"}, JSON.stringify({
    score: [
      {
        id: 1,
        name: 'score 1'
      }
    ],
    levels: levels
  })];
});

However, I still get the same error.

Any ideas? How would I debug this issue?

Assorted versions:

Ember CLI: 0.1.12
Node: 0.10.33
NPM: 2.1.8
Ember: 1.10.0
Ember Data: 1.0.0-beta.15
Ember CLI Pretender: 0.3.1
Pretender: 0.6.0
Handlebars: 2.0.0
HTMLBars: ^0.7.4