diff --git a/includes/common.inc b/includes/common.inc
index d34c19d..fa33dfe 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -6138,6 +6138,9 @@ function element_child($key) {
 /**
  * Return the children of an element, optionally sorted by weight.
  *
+ * The children of a given array are those elements that have a key that
+ * does not start with a '#'. See drupal_render() for details.
+ *
  * @param $elements
  *   The element to be sorted.
  * @param $sort