diff --git a/includes/lock.inc b/includes/lock.inc
index 7dd8db30a16..db8456187ac 100644
--- a/includes/lock.inc
+++ b/includes/lock.inc
@@ -92,7 +92,7 @@ function _lock_id() {
  * Acquire (or renew) a lock, but do not block if it fails.
  *
  * @param $name
- *   The name of the lock.
+ *   The name of the lock. Limit of name's length is 255 characters.
  * @param $timeout
  *   A number of seconds (float) before the lock expires (minimum of 0.001).
  *