diff --git a/core/modules/filter/filter.module b/core/modules/filter/filter.module
index 1e858ad..e7cbdd7 100644
--- a/core/modules/filter/filter.module
+++ b/core/modules/filter/filter.module
@@ -344,8 +344,8 @@ function filter_format_allowcache($format_id) {
  * @param $text
  *   The text to be filtered.
  * @param $format_id
- *   (optional) The format ID of the text to be filtered. If no format is
- *   assigned, the fallback format will be used. Defaults to NULL.
+ *   (optional) The machine name of the filter format to be used to filter the
+ *   text. Defaults to the fallback format. See filter_fallback_format().
  * @param $langcode
  *   (optional) The language code of the text to be filtered, e.g. 'en' for
  *   English. This allows filters to be language aware so language specific