diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index 7ceff7b693..10dddf859b 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -2591,7 +2591,9 @@ function unregister_post_meta( $post_type, $meta_key ) {
  * @since 1.2.0
  *
  * @param int $post_id Optional. Post ID. Default is the ID of the global `$post`.
- * @return array Post meta for the given post.
+ * @return mixed An array of values.
+ *               False for an invalid `$post_id` (non-numeric, zero, or negative value).
+ *               An empty string if a valid but non-existing post ID is passed.
  */
 function get_post_custom( $post_id = 0 ) {
 	$post_id = absint( $post_id );