diff --git a/inc/abstractitiltarget.class.php b/inc/abstractitiltarget.class.php
index 011c3dbfe..46986f339 100644
--- a/inc/abstractitiltarget.class.php
+++ b/inc/abstractitiltarget.class.php
@@ -2221,6 +2221,9 @@ protected function prepareUploadedFiles(array $data, $formanswer): array {
             if (!($field instanceOf FileField)) {
                continue;
             }
+            if (!isset($saved_documents["_filename"][$questionId])) {
+               continue;
+            }
             $data["_filename"] = array_merge($data["_filename"], $saved_documents["_filename"][$questionId] ?? []);
             $data["_tag_filename"] = array_merge($data["_tag_filename"], $saved_documents["_tag_filename"][$questionId] ?? []);