diff --git a/externallib.php b/externallib.php
index d2c3bf6..64a9155 100644
--- a/externallib.php
+++ b/externallib.php
@@ -22,6 +22,11 @@
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 
+use core_external\external_api;
+use core_external\external_function_parameters;
+use core_external\external_single_structure;
+use core_external\external_value;
+
 defined('MOODLE_INTERNAL') || die;   
 
 /**