diff --git a/CRM/Event/BAO/Event.php b/CRM/Event/BAO/Event.php
index 09f06ac9cc7a..ec9d0e6b485d 100644
--- a/CRM/Event/BAO/Event.php
+++ b/CRM/Event/BAO/Event.php
@@ -1143,6 +1143,15 @@ public static function sendMail($contactID, $values, $participantId, $isTest = F
 
         // @todo - the goal is that all params available to the message template are explicitly defined here rather than
         // 'in a smattering of places'. Note that leakage can happen between mailings when not explicitly defined.
+        if ($postProfileID) {
+          $customPostTitles = empty($profilePost[1]) ? NULL : [];
+          foreach ($postProfileID as $offset => $id) {
+            $customPostTitles[$offset] = CRM_Core_BAO_UFGroup::getFrontEndTitle((int) $id);
+          }
+        }
+        else {
+          $customPostTitles = NULL;
+        }
         $tplParams = array_merge($values, $participantParams, [
           'email' => $email,
           'confirm_email_text' => CRM_Utils_Array::value('confirm_email_text', $values['event']),
@@ -1152,7 +1161,7 @@ public static function sendMail($contactID, $values, $participantId, $isTest = F
           'customPre' => $profilePre[0],
           'customPre_grouptitle' => empty($profilePre[1]) ? NULL : [CRM_Core_BAO_UFGroup::getFrontEndTitle((int) $preProfileID)],
           'customPost' => $profilePost[0],
-          'customPost_grouptitle' => empty($profilePost[1]) ? NULL : [CRM_Core_BAO_UFGroup::getFrontEndTitle((int) $postProfileID)],
+          'customPost_grouptitle' => $customPostTitles,
           'participantID' => $participantId,
           'conference_sessions' => $sessions,
           'credit_card_number' => CRM_Utils_System::mungeCreditCard(CRM_Utils_Array::value('credit_card_number', $participantParams)),