diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index 40f8870d77..a4f321fb3a 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -267,8 +267,10 @@ function image_downsize( $id, $size = 'medium' ) {
  * @param string     $name   Image size identifier.
  * @param int        $width  Optional. Image width in pixels. Default 0.
  * @param int        $height Optional. Image height in pixels. Default 0.
- * @param bool|array $crop   Optional. Whether to crop images to specified width and height or resize.
- *                           An array can specify positioning of the crop area. Default false.
+ * @param bool|array $crop   Optional. If true, images will be cropped without any adjustments
+ *                           in dimensions. Otherwise try to adjust images dimensions
+ *                           according specified width and height parameters before cropping it.
+ *                           Extended description could be found in the function summary.
  */
 function add_image_size( $name, $width = 0, $height = 0, $crop = false ) {
 	global $_wp_additional_image_sizes;