diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index b5327ed788..0050d10b7c 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -3172,8 +3172,9 @@ function wp_list_filter( $list, $args = array(), $operator = 'AND' ) {
  * @param int|string $field     Field from the object to place instead of the entire object
  * @param int|string $index_key Optional. Field from the object to use as keys for the new array.
  *                              Default null.
- * @return array Array of found values. If $index_key is set, an array of found values with keys
- *               corresponding to $index_key.
+ * @return array Array of found values. If `$index_key` is set, an array of found values with keys
+ *               corresponding to `$index_key`. If `$index_key` is null, array keys from the original
+ *               `$list` will be preserved in the results.
  */
 function wp_list_pluck( $list, $field, $index_key = null ) {
 	if ( ! $index_key ) {