diff --git a/src/lib/Server/Output/ValueObjectVisitor/Version.php b/src/lib/Server/Output/ValueObjectVisitor/Version.php
index 0aed9390..4e507f28 100644
--- a/src/lib/Server/Output/ValueObjectVisitor/Version.php
+++ b/src/lib/Server/Output/ValueObjectVisitor/Version.php
@@ -136,7 +136,7 @@ private function visitThumbnail(
     ): void {
         $generator->startObjectElement('Thumbnail');
 
-        if (!empty($thumbnail)) {
+        if (!empty($thumbnail->resource)) {
             $generator->startValueElement('resource', $thumbnail->resource);
             $generator->endValueElement('resource');