diff --git a/Form/EventListener/SingleUploadSubscriber.php b/Form/EventListener/SingleUploadSubscriber.php
index 9a0eacb..a881bc3 100644
--- a/Form/EventListener/SingleUploadSubscriber.php
+++ b/Form/EventListener/SingleUploadSubscriber.php
@@ -149,7 +149,7 @@ public function postSubmit(FormEvent $event): void
         }
     }
     
-    private function isFieldSingleUpload(ResolvedFormTypeInterface $formTypeInterface = null): bool
+    private function isFieldSingleUpload(?ResolvedFormTypeInterface $formTypeInterface = null): bool
     {
         if ($formTypeInterface == null) {
             return false;
diff --git a/Storage/FileStorageInterface.php b/Storage/FileStorageInterface.php
index 05d51a9..8431f90 100644
--- a/Storage/FileStorageInterface.php
+++ b/Storage/FileStorageInterface.php
@@ -7,5 +7,5 @@ interface FileStorageInterface
 {
     public function storeFiles(array $files): array;
 
-    public function getFile(string $fileId = null): ?UploadedFile;
+    public function getFile(?string $fileId = null): ?UploadedFile;
 }
diff --git a/Storage/LocalFileStorage.php b/Storage/LocalFileStorage.php
index 27ae351..a67f57b 100644
--- a/Storage/LocalFileStorage.php
+++ b/Storage/LocalFileStorage.php
@@ -18,7 +18,7 @@ class LocalFileStorage implements FileStorageInterface
 
     private SessionInterface $session;
 
-    public function __construct(private readonly RequestStack $requestStack, string $tempDir = null)
+    public function __construct(private readonly RequestStack $requestStack, ?string $tempDir = null)
     {
         $this->temporaryDirectory = $tempDir ?: sys_get_temp_dir() . DIRECTORY_SEPARATOR . 's2a' . DIRECTORY_SEPARATOR . 'collectionupload';
     }
@@ -52,7 +52,7 @@ public function storeFiles(array $files): array
         return $handledFiles;
     }
 
-    public function getFile(string $fileId = null): ?UploadedFile
+    public function getFile(?string $fileId = null): ?UploadedFile
     {
         if (is_null($fileId)) {
             return null;