diff --git a/src/global_functions.php b/src/global_functions.php
index d040de9..0fb17b7 100644
--- a/src/global_functions.php
+++ b/src/global_functions.php
@@ -69,7 +69,9 @@ function mdShortenerExceptionHandler(Throwable $exception):void {
     $errorReporter = new MDErrorReporter("md:frontend", "bugs-frontend@museum-digital.de");
     $errorCategory = MDErrorReporter::categorizeError($exception);
 
-    http_response_code(404);
+    if (headers_sent() === false) {
+        http_response_code(404);
+    }
 
     switch ($errorCategory) {
     case MDErrorReporter::MD_ERROR_KNOWN: