diff --git a/lib/classes/oauth2/user_field_mapping.php b/lib/classes/oauth2/user_field_mapping.php
index cecbc9e84df..9b73bdf5656 100644
--- a/lib/classes/oauth2/user_field_mapping.php
+++ b/lib/classes/oauth2/user_field_mapping.php
@@ -43,6 +43,8 @@ class user_field_mapping extends persistent {
      * @return array
      */
     private static function get_user_fields() {
+        global $CFG;
+        require_once($CFG->dirroot . '/user/profile/lib.php');
         return array_merge(\core_user::AUTHSYNCFIELDS, ['picture', 'username'], get_profile_field_names());
     }
 
@@ -72,6 +74,8 @@ class user_field_mapping extends persistent {
      * @return array
      */
     public function get_internalfield_list() {
+        global $CFG;
+        require_once($CFG->dirroot . '/user/profile/lib.php');
         $userfields = array_merge(\core_user::AUTHSYNCFIELDS, ['picture', 'username']);
         $internalfields = array_combine($userfields, $userfields);
         return array_merge(['' => $internalfields], get_profile_field_list());