diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index 71505aee0f..7e7afc029a 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -707,8 +707,8 @@ function get_intermediate_image_sizes() {
  * @since 2.5.0
  *
  * @param int          $attachment_id Image attachment ID.
- * @param string|array $size          Optional. Registered image size to retrieve the source for or a flat
- *                                    array of height and width dimensions. Default 'thumbnail'.
+ * @param string|array $size          Optional. Image size. Accepts any valid image size, or an array of width
+ *                                    and height values in pixels (in that order). Default 'thumbnail'.
  * @param bool         $icon          Optional. Whether the image should be treated as an icon. Default false.
  * @return false|array Returns an array (url, width, height, is_intermediate), or false, if no image is available.
  */