diff --git a/Classes/Controller/AiImageController.php b/Classes/Controller/AiImageController.php
index 5b1e693..96465df 100644
--- a/Classes/Controller/AiImageController.php
+++ b/Classes/Controller/AiImageController.php
@@ -264,7 +264,7 @@ public function upscaleAction(File $file): void
         $this->redirect('filelist');
     }
 
-    public function extendAction(string $direction, File $file = null, string $base64 = ''): void
+    public function extendAction(string $direction, ?File $file = null, string $base64 = ''): void
     {
         try {
             $filePath = '';
diff --git a/Classes/Http/Client/AltTextClient.php b/Classes/Http/Client/AltTextClient.php
index 41358e8..5c2774e 100644
--- a/Classes/Http/Client/AltTextClient.php
+++ b/Classes/Http/Client/AltTextClient.php
@@ -49,7 +49,7 @@ private function getAuthorizationHeader(): array
         ];
     }
 
-    public function getAltTextForFile(File $file, string $languageIsoCode = null): string
+    public function getAltTextForFile(File $file, ?string $languageIsoCode = null): string
     {
         $localFile = $file->getOriginalResource()->getForLocalProcessing();
 
@@ -81,7 +81,7 @@ public function getAltTextForFile(File $file, string $languageIsoCode = null): s
         return $response->alt_text;
     }
 
-    public function getByAssetId(int $assetId, string $languageIsoCode = null): string
+    public function getByAssetId(int $assetId, ?string $languageIsoCode = null): string
     {
         if (null === $languageIsoCode) {
             $languageIsoCode = $this->siteLanguageService->getLanguage();
diff --git a/Classes/Service/AiAltTextService.php b/Classes/Service/AiAltTextService.php
index b607ed7..4bc33be 100644
--- a/Classes/Service/AiAltTextService.php
+++ b/Classes/Service/AiAltTextService.php
@@ -32,7 +32,7 @@ public function __construct(AltTextClient $altTextClient)
     /**
      * @throws \Exception
      */
-    public function getAltText(File $file, string $languageIsoCode = null): string
+    public function getAltText(File $file, ?string $languageIsoCode = null): string
     {
         try {
             $altText = $this->altTextClient->getByAssetId($file->getOriginalResource()->getUid(), $languageIsoCode);
diff --git a/Classes/Service/ExtendService.php b/Classes/Service/ExtendService.php
index c2b46c0..e5441b9 100644
--- a/Classes/Service/ExtendService.php
+++ b/Classes/Service/ExtendService.php
@@ -81,7 +81,7 @@ public function resolutionForExtendedImage(string $sourceImagePath, string $dire
      *
      * @throws \Exception
      */
-    private function getImageDimensions($source = null, string $imagePath = null): array
+    private function getImageDimensions($source = null, ?string $imagePath = null): array
     {
         $width = null;
         $height = null;
diff --git a/Classes/Service/FileService.php b/Classes/Service/FileService.php
index 379de25..f4c6e93 100644
--- a/Classes/Service/FileService.php
+++ b/Classes/Service/FileService.php
@@ -31,7 +31,7 @@ class FileService
 
     private string $path = 'mkcontentai';
 
-    public function __construct(string $folder = null)
+    public function __construct(?string $folder = null)
     {
         $this->path = 'mkcontentai/'.$folder;
         $this->storageRepository = GeneralUtility::makeInstance(StorageRepository::class);