diff --git a/Modules/Survey/classes/class.ilObjSurvey.php b/Modules/Survey/classes/class.ilObjSurvey.php
index 2c7ff7ff66e9..8a44c6b247d1 100755
--- a/Modules/Survey/classes/class.ilObjSurvey.php
+++ b/Modules/Survey/classes/class.ilObjSurvey.php
@@ -3725,9 +3725,9 @@ public function getSurveyCodesTableData(
 
                 if ($row["externaldata"]) {
                     $ext = unserialize((string) $row["externaldata"], ['allowed_classes' => false]);
-                    $item['email'] = $ext['email'];
-                    $item['last_name'] = $ext['lastname'];
-                    $item['first_name'] = $ext['firstname'];
+                    $item['email'] = $ext['email'] ?? "";
+                    $item['last_name'] = $ext['lastname'] ?? "";
+                    $item['first_name'] = $ext['firstname'] ?? "";
                 }
 
                 $codes[] = $item;