diff --git a/includes/cache.inc b/includes/cache.inc
index bba654e..3bd5e49 100644
--- a/includes/cache.inc
+++ b/includes/cache.inc
@@ -126,9 +126,9 @@ function cache_set($cid, $data, $table = 'cache', $expire = CACHE_PERMANENT, $he
  *   argument if $cid is set.
  *
  * @param $wildcard
- *   If set to TRUE, the $cid is treated as a substring
- *   to match rather than a complete ID. The match is a right hand
- *   match. If '*' is given as $cid, the table $table will be emptied.
+ *   If $wildcard is TRUE, all cache IDs having $cid as a prefix are
+ *   deleted.  If $wildcard is TRUE and $cid is '*' then the
+ *   table $table is emptied.
  */
 function cache_clear_all($cid = NULL, $table = NULL, $wildcard = FALSE) {
   global $user;