Vows breaks on nested topics

gistfile1.js

(function () {
  'use strict';
  
  var vows = require('vows'),
      assert = require('assert');

  vows.describe('some test').addBatch({
    'test level 1': {
      topic: function () {
        this.callback(null, 1);
      },
      'is it 1?': function (one) {
        assert.equal(one, 1);
      },
      'test level 2': {
        topic: function (one) {
          this.callback(2, one);
        },
        'is it 2?': function (two, one) {
          assert.equal(two, 2);
          assert.equal(one, 1);
        },
        'test level 3': {
          topic: function (two, one) {
            this.callback(3, two, one);
          },
          'is it 3?': function (three, two, one) {
            assert.equal(three, 3);
            assert.equal(two, 2);
            assert.equal(one, 1);
          },
          'test level 4': {
            topic: function (three, two, one) {
              this.callback(5, three, two, one);
            },
            'is it 5?': function (five, three, two, one) {
              assert.equal(five, 5);
              assert.equal(three, 3);
              assert.equal(two, 2);
              assert.equal(one, 1);
            }
          }
        }
      }
    }
  }).run();

}());