diff --git a/classes/frontend.php b/classes/frontend.php
index b9d0107..84c26f4 100644
--- a/classes/frontend.php
+++ b/classes/frontend.php
@@ -45,7 +45,7 @@ protected function get_javascript_strings() {
      * @param  \section_info $section Section currently being edited (null if none)
      * @return array Array of parameters for the JavaScript function
      */
-    protected function get_javascript_init_params($course, \cm_info $cm = null, \section_info $section = null) {
+    protected function get_javascript_init_params($course, ?\cm_info $cm = null, ?\section_info $section = null) {
         $context = \context_course::instance($course->id);
         $participants = get_enrolled_users($context, '', 0, 'u.*', 'lastname, firstname');
         $participantlist = [];