diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index 078d9f5..926fd2c 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -1819,6 +1819,8 @@ function hook_permission() {
  *     'module', 'theme_engine', or 'theme'.
  *   - theme path: (automatically derived) The directory path of the theme or
  *     module, so that it doesn't need to be looked up.
+ *
+ * @see hook_theme_registry_alter()
  */
 function hook_theme($existing, $type, $theme, $path) {
   return array(