diff --git a/Classes/Controller/Backend/Search/CoreOptimizationModuleController.php b/Classes/Controller/Backend/Search/CoreOptimizationModuleController.php
index d8bcfe51fb..da94c219d4 100644
--- a/Classes/Controller/Backend/Search/CoreOptimizationModuleController.php
+++ b/Classes/Controller/Backend/Search/CoreOptimizationModuleController.php
@@ -277,7 +277,6 @@ protected function exportFile(string $content, string $type = 'synonyms', string
             ->withHeader('Content-Type', 'text/plain; charset=utf-8')
             ->withHeader('Cache-control', 'public')
             ->withHeader('Content-Description', 'File transfer')
-            ->withHeader('Content-Description', 'File transfer')
             ->withHeader(
                 'Content-disposition',
                 'attachment; filename =' . $type . '_' . $coreAdmin->getPrimaryEndpoint()->getCore() . '.' . $fileExtension