diff --git a/calendar/classes/local/event/forms/managesubscriptions.php b/calendar/classes/local/event/forms/managesubscriptions.php
index 102761f7116..61ef73f087c 100644
--- a/calendar/classes/local/event/forms/managesubscriptions.php
+++ b/calendar/classes/local/event/forms/managesubscriptions.php
@@ -40,6 +40,7 @@ class managesubscriptions extends \moodleform {
      * Defines the form used to add calendar subscriptions.
      */
     public function definition() {
+        global $PAGE;
         $mform = $this->_form;
         $eventtypes = calendar_get_allowed_event_types();
         if (in_array(true, $eventtypes, true) === false) {
@@ -86,6 +87,9 @@ class managesubscriptions extends \moodleform {
 
         // Eventtype: 0 = user, 1 = global, anything else = course ID.
         $mform->addElement('submit', 'add', get_string('add'));
+
+        // Add the javascript required to enhance this mform.
+        $PAGE->requires->js_call_amd('core_calendar/event_form', 'init', [$mform->getAttribute('id')]);
     }
 
     /**
diff --git a/calendar/lib.php b/calendar/lib.php
index a91e4f2eca8..2e78d15b6b5 100644
--- a/calendar/lib.php
+++ b/calendar/lib.php
@@ -2783,14 +2783,6 @@ function calendar_add_subscription($sub) {
         unset($sub->groupcourseid);
     }
 
-    // Pull the group id back out of the value. The form saves the value
-    // as "<courseid>-<groupid>" to allow the javascript to work correctly.
-    if (!empty($sub->groupid)) {
-        list($courseid, $groupid) = explode('-', $sub->groupid);
-        $sub->courseid = $courseid;
-        $sub->groupid = $groupid;
-    }
-
     // Default course id if none is set.
     if (empty($sub->courseid)) {
         if ($sub->eventtype === 'site') {
diff --git a/calendar/managesubscriptions.php b/calendar/managesubscriptions.php
index 87289a6c9be..93457043525 100644
--- a/calendar/managesubscriptions.php
+++ b/calendar/managesubscriptions.php
@@ -33,6 +33,7 @@ $categoryid = optional_param('category', null, PARAM_INT);
 // Used for processing subscription actions.
 $subscriptionid = optional_param('id', 0, PARAM_INT);
 $pollinterval  = optional_param('pollinterval', 0, PARAM_INT);
+$groupcourseid  = optional_param('groupcourseid', 0, PARAM_INT);
 $action = optional_param('action', '', PARAM_INT);
 
 $url = new moodle_url('/calendar/managesubscriptions.php');
@@ -61,7 +62,22 @@ if (!calendar_user_can_add_event($course)) {
     print_error('errorcannotimport', 'calendar');
 }
 
-$form = new \core_calendar\local\event\forms\managesubscriptions(null, ['courseid' => $course->id]);
+// Populate the 'group' select box based on the given 'groupcourseid', if necessary.
+$groups = [];
+if (!empty($groupcourseid)) {
+    require_once($CFG->libdir . '/grouplib.php');
+    $groupcoursedata = groups_get_course_data($groupcourseid);
+    if (!empty($groupcoursedata->groups)) {
+        foreach ($groupcoursedata->groups as $groupid => $groupdata) {
+            $groups[$groupid] = $groupdata->name;
+        }
+    }
+}
+$customdata = [
+    'courseid' => $course->id,
+    'groups' => $groups,
+];
+$form = new \core_calendar\local\event\forms\managesubscriptions(null, $customdata);
 $form->set_data(array(
     'course' => $course->id
 ));
diff --git a/calendar/tests/events_test.php b/calendar/tests/events_test.php
index 5750d507f55..76f8374effc 100644
--- a/calendar/tests/events_test.php
+++ b/calendar/tests/events_test.php
@@ -533,7 +533,8 @@ class core_calendar_events_testcase extends advanced_testcase {
         $subscription = new stdClass();
         $subscription->eventtype = 'group';
         $subscription->name = 'test';
-        $subscription->groupid = "{$courseid}-{$groupid}";
+        $subscription->courseid = $courseid;
+        $subscription->groupid = $groupid;
 
         // Trigger and capture the event.
         $sink = $this->redirectEvents();
@@ -668,7 +669,9 @@ class core_calendar_events_testcase extends advanced_testcase {
         $subscription = new stdClass();
         $subscription->eventtype = 'group';
         $subscription->name = 'test';
-        $subscription->groupid = "{$courseid}-{$groupid}";
+        $subscription->courseid = $courseid;
+        $subscription->groupid = $groupid;
+
         $subscription->id = calendar_add_subscription($subscription);
         // Now edit it.
         $subscription->name = 'awesome';
@@ -797,7 +800,8 @@ class core_calendar_events_testcase extends advanced_testcase {
         $subscription = new stdClass();
         $subscription->eventtype = 'group';
         $subscription->name = 'test';
-        $subscription->groupid = "{$courseid}-{$groupid}";
+        $subscription->groupid = $groupid;
+        $subscription->courseid = $courseid;
         $subscription->id = calendar_add_subscription($subscription);
 
         // Trigger and capture the event.