diff --git a/lib/Kronolith.php b/lib/Kronolith.php
index 6282754a4..b2b497611 100644
--- a/lib/Kronolith.php
+++ b/lib/Kronolith.php
@@ -2137,16 +2137,18 @@ public static function sendNotification($event, $action)
 
         $owner = $share->get('owner');
         if ($owner) {
-            $recipients[$owner] = self::_notificationPref($owner, 'owner');
-            $recipients[$owner]['private'] = $event->isPrivate($owner);
+            if ($notificationPrefs = self::_notificationPref($owner, 'owner')) {
+                $recipients[$owner] = $notificationPrefs;
+                $recipients[$owner]['private'] = $event->isPrivate($owner);
+            }
         }
 
         $senderIdentity = $injector->getInstance('Horde_Core_Factory_Identity')
             ->create($registry->getAuth() ?: $event->creator ?: $owner);
 
         foreach ($share->listUsers(Horde_Perms::READ) as $user) {
-            if (empty($recipients[$user])) {
-                $recipients[$user] = self::_notificationPref($user, 'read', $calendar);
+            if (empty($recipients[$user]) && ($notificationPrefs = self::_notificationPref($user, 'read', $calendar))) {
+                $recipients[$user] = $notificationPrefs;
                 $recipients[$user]['private'] = $event->isPrivate($user);
             }
         }
@@ -2160,8 +2162,8 @@ public static function sendNotification($event, $action)
             }
 
             foreach ($group_users as $user) {
-                if (empty($recipients[$user])) {
-                    $recipients[$user] = self::_notificationPref($user, 'read', $calendar);
+            if (empty($recipients[$user]) && ($notificationPrefs = self::_notificationPref($user, 'read', $calendar))) {
+                    $recipients[$user] = $notificationPrefs;
                     $recipients[$user]['private'] = $event->isPrivate($user);
                 }
             }