Error message when organizing migrations into groups as per advanced example

I'm new to Migrate, and am trying to set up a migration closely based on the example advanced migration (Wine). The Wine migration has two migration classes (abstract class AdvancedExampleMigration and class WinePrepMigration) that call the parent constructor like so:

parent::__construct(MigrateGroup::getInstance('wine', array('default')));

This seems to work fine in the example, but when I duplicate the code in my own module, and visit /admin/content/migrate, I get the following error message:

MigrateException: Failure to sort migration list - most likely due to circular dependencies involving groups wine in MigrateGroup::groups() (line 55 of /srv/www/pixelscrapper/public_html/sites/all/modules/contrib/migrate/includes/group.inc).

The error goes away when I remove the arguments from the second constructor, and replace it simply with "parent::__construct();"

I'm a bit baffled why this code is running okay in the example, but not when I copy it exactly to my own module?

Here's the code I have in my custom module's inc file, that is throwing the error (copied directly from Wine.inc, have only changed the class names):

abstract class AssetMigration extends Migration {
  public $basicFormat;

  public function __construct() {
    // TIP: Migrations can be organized into groups. In this case, all the migrations
    // derived from AdvancedExampleMigration will be part of the 'wine' group.
    // This enables us to easily run just the wine example migrations:
    //  drush migrate-import --group=wine
    // The second argument to MigrateGroup::getInstance is an array of groups
    // which should come before this when viewing migration statuses, or running
    // migration operations using --all. Since the beer migrations in this module
    // did not specify a group, it is in the 'default' group, so this constructor
    // indicates that the wine migrations come after the beer migrations.
    parent::__construct(MigrateGroup::getInstance('wine', array('default')));

    $this->team = array(
      new MigrateTeamMember('Jack Kramer', 'jkramer@example.com', t('Taster')),
      new MigrateTeamMember('Linda Madison', 'lmadison@example.com', t('Winemaker')),
    );
    $this->issuePattern = 'http://drupal.org/node/:id:';

    // A format of our own, for testing migration of formats
    $this->basicFormat = filter_format_load('migrate_example');
  }
}

/**
 * TIP: While usually you'll create true migrations - processes that copy data
 * from some source into Drupal - you can also define processing steps for either
 * the import or rollback stages that take other actions. In this case, we want
 * to disable auto_nodetitle while the migration steps run.
 */
class AssetPrepMigration extends MigrationBase {
  // Remember whether the auto_nodetitle was originally enabled, so we know whether
  // to re-enable it
  public static $wasEnabled = FALSE;

  public function __construct() {
    // Because we're derived directly from migrationBase rather than AdvancedExampleMigration,
    // we must specify the group again here.
    parent::__construct(MigrateGroup::getInstance('wine', array('default')));
    $this->description = t('If auto_nodetitle is present, disable it for the duration');
  }
  // Define isComplete(), returning a boolean, to indicate whether dependent
  // migrations may proceed
  public function isComplete() {
    // If Auto Node Title is disabled, other migrations are free to go
    if (module_exists('auto_nodetitle')) {
      return FALSE;
    }
    else {
      return TRUE;
    }
  }
  // Implement any action you want to occur during an import process in an
  // import() method (alternatively, if you have an action which you want to
  // run during rollbacks, define a rollback() method).
  public function import() {
    if (module_exists('auto_nodetitle')) {
      self::$wasEnabled = TRUE;
      module_disable(array('auto_nodetitle'));
      $this->showMessage(t('Disabled auto_nodetitle module'), 'success');
    }
    else {
      self::$wasEnabled = FALSE;
      $this->showMessage(t('Auto_nodetitle is already disabled'), 'success');
    }
    // Must return one of the MigrationBase RESULT constants
    return MigrationBase::RESULT_COMPLETED;
  }
}

Any help is appreciated!