diff --git a/modules/image/image.module b/modules/image/image.module
index 066bd34..ce63eeb 100644
--- a/modules/image/image.module
+++ b/modules/image/image.module
@@ -593,9 +593,22 @@ function image_style_load($name = NULL, $isid = NULL, $include = NULL) {
  * Save an image style.
  *
  * @param style
- *   An image style array.
+ *   An image style array. The corresponding array may contain the following
+ *   key-value pairs:
+ *   - "isid": (optional) If isid is not specified, a new image style will be
+ *   created. If specified, the associated image style will be updated.
+ *   - "name": The unique name of the image style.
+ *   - "storage": How the image style is stored. See IMAGE_STORAGE_DEFAULT.
+ *   - "effects": An image effects array. See image_style_effects().
  * @return
  *   An image style array. In the case of a new style, 'isid' will be populated.
+ *   The corresponding array may contain the following key-value pairs:
+ *   - "isid": Unique ID of the image style.
+ *   - "name": Unique name of the image style.
+ *   - "storage": How the image style is stored. See IMAGE_STORAGE_DEFAULT.
+ *   - "effects": An image effects array. See image_style_effects().
+ *   - "old_name": If name was updated this will contain the old name.
+ *   - "is_new": True, if new image style.
  */
 function image_style_save($style) {
   if (isset($style['isid']) && is_numeric($style['isid'])) {