diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index 1dbf0c9867..1dab926aea 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -1770,7 +1770,9 @@ function delete_post_meta( $post_id, $meta_key, $meta_value = '' ) {
  * @param int    $post_id Post ID.
  * @param string $key     Optional. The meta key to retrieve. By default, returns
  *                        data for all keys. Default empty.
- * @param bool   $single  Optional. Whether to return a single value. Default false.
+ * @param bool   $single  Optional, default is false.
+ *                        If true, return only the first value of the specified meta_key.
+ *                        This parameter has no effect if meta_key is not specified.
  * @return mixed Will be an array if $single is false. Will be value of meta data
  *               field if $single is true.
  */