diff --git a/calendar/managesubscriptions.php b/calendar/managesubscriptions.php
index 9c6af0adacc..91fbf6595cd 100644
--- a/calendar/managesubscriptions.php
+++ b/calendar/managesubscriptions.php
@@ -37,7 +37,7 @@ $groupcourseid  = optional_param('groupcourseid', 0, PARAM_INT);
 $action = optional_param('action', '', PARAM_INT);
 
 $url = new moodle_url('/calendar/managesubscriptions.php');
-if ($courseid != SITEID) {
+if ($courseid != SITEID && !empty($courseid)) {
     $url->param('course', $courseid);
 }
 if ($categoryid) {
@@ -77,7 +77,7 @@ $customdata = [
     'courseid' => $course->id,
     'groups' => $groups,
 ];
-$form = new \core_calendar\local\event\forms\managesubscriptions(null, $customdata);
+$form = new \core_calendar\local\event\forms\managesubscriptions($url, $customdata);
 $form->set_data(array(
     'course' => $course->id
 ));
diff --git a/calendar/renderer.php b/calendar/renderer.php
index a590cdfaf7b..314ecaf86a4 100644
--- a/calendar/renderer.php
+++ b/calendar/renderer.php
@@ -374,7 +374,7 @@ class core_calendar_renderer extends plugin_renderer_base {
      */
     protected function subscription_action_form($subscription) {
         // Assemble form for the subscription row.
-        $html = html_writer::start_tag('form', array('action' => new moodle_url('/calendar/managesubscriptions.php'), 'method' => 'post'));
+        $html = html_writer::start_tag('form', ['action' => $this->page->url->out(false) , 'method' => 'post']);
         if (empty($subscription->url)) {
             // Don't update an iCal file, which has no URL.
             $html .= html_writer::empty_tag('input', array('type' => 'hidden', 'name' => 'pollinterval', 'value' => '0'));