diff --git a/enrol/manual/ajax.php b/enrol/manual/ajax.php
index a78f19c2595..5f21c654ec0 100644
--- a/enrol/manual/ajax.php
+++ b/enrol/manual/ajax.php
@@ -65,7 +65,7 @@ switch ($action) {
         $enrolid = required_param('enrolid', PARAM_INT);
         $cohorts = $users = [];
 
-        $userids = optional_param('userlist', [], PARAM_SEQUENCE);
+        $userids = optional_param_array('userlist', [], PARAM_SEQUENCE);
         $userid = optional_param('userid', 0, PARAM_INT);
         if ($userid) {
             $userids[] = $userid;
@@ -75,7 +75,7 @@ switch ($action) {
                 $users[] = $DB->get_record('user', array('id' => $userid), '*', MUST_EXIST);
             }
         }
-        $cohortids = optional_param('cohortlist', [], PARAM_SEQUENCE);
+        $cohortids = optional_param_array('cohortlist', [], PARAM_SEQUENCE);
         $cohortid = optional_param('cohortid', 0, PARAM_INT);
         if ($cohortid) {
             $cohortids[] = $cohortid;