diff --git a/src/applications/calendar/notifications/PhabricatorCalendarNotificationEngine.php b/src/applications/calendar/notifications/PhabricatorCalendarNotificationEngine.php
--- a/src/applications/calendar/notifications/PhabricatorCalendarNotificationEngine.php
+++ b/src/applications/calendar/notifications/PhabricatorCalendarNotificationEngine.php
@@ -100,10 +100,11 @@
         }
         $notifiable_phids[] = $invitee->getInviteePHID();
       }
-      if (!$notifiable_phids) {
+      if ($notifiable_phids) {
+        $attendee_map[$key] = array_fuse($notifiable_phids);
+      } else {
         unset($events[$key]);
       }
-      $attendee_map[$key] = array_fuse($notifiable_phids);
     }
     if (!$attendee_map) {
       // None of the events have any notifiable attendees, so there is no