diff --git a/src/Form/Type/FileUploadType.php b/src/Form/Type/FileUploadType.php
index e78d3bef1e..df7e9e5c64 100644
--- a/src/Form/Type/FileUploadType.php
+++ b/src/Form/Type/FileUploadType.php
@@ -159,7 +159,7 @@ public function configureOptions(OptionsResolver $resolver): void
                 return strtr($fileNamePatternOrCallable, [
                     '[contenthash]' => sha1_file($file->getRealPath()),
                     '[day]' => date('d'),
-                    '[extension]' => $file->guessClientExtension(),
+                    '[extension]' => $file->guessExtension(),
                     '[month]' => date('m'),
                     '[name]' => pathinfo($file->getClientOriginalName(), \PATHINFO_FILENAME),
                     '[randomhash]' => bin2hex(random_bytes(20)),