diff --git a/src/lib/Service/ContentService.php b/src/lib/Service/ContentService.php
index 86aafff0..b41be9b2 100644
--- a/src/lib/Service/ContentService.php
+++ b/src/lib/Service/ContentService.php
@@ -259,9 +259,9 @@ private function getAuthor(APIContent $contentValue, APIContentType $contentType
      *
      * @return array<string>
      */
-    private function prepareFields(APIContentType $contentType, array $fields): array
+    private function prepareFields(APIContentType $contentType, ?array $fields = null): array
     {
-        if (empty($fields)) {
+        if (!empty($fields)) {
             return $fields;
         }