define('FILTER_FORMAT_DEFAULT', 0)
In Drupal 7, you'll need to replace this with either http://api.drupal.org/api/function/filter_fallback_format/7 (fallback default for everyone) or http://api.drupal.org/api/function/filter_default_format/7 (user-specific default), depending on your use case.
See http://drupal.org/node/633974 for one example where this was fixed.
Comments
No longer in Drupal 7
In Drupal 7, you'll need to replace this with either http://api.drupal.org/api/function/filter_fallback_format/7 (fallback default for everyone) or http://api.drupal.org/api/function/filter_default_format/7 (user-specific default), depending on your use case.
See http://drupal.org/node/633974 for one example where this was fixed.