diff --git a/Services/NotificationService.php b/Services/NotificationService.php
index 7219dce..0e01549 100644
--- a/Services/NotificationService.php
+++ b/Services/NotificationService.php
@@ -31,7 +31,7 @@ public function __construct(
         DocumentManager $documentManager,
         YoutubeConfigurationService $youtubeConfigurationService,
         TagService $tagService,
-        SenderService $senderService = null,
+        ?SenderService $senderService = null,
         LoggerInterface $logger,
         RouterInterface $router,
         TranslatorInterface $translator,
diff --git a/Services/VideoDataValidationService.php b/Services/VideoDataValidationService.php
index 9fa8719..deba52b 100644
--- a/Services/VideoDataValidationService.php
+++ b/Services/VideoDataValidationService.php
@@ -37,7 +37,7 @@ public function __construct(
         YoutubeConfigurationService $youtubeConfigurationService,
         JobService $jobService,
         TagService $tagService,
-        OpencastService $opencastService = null,
+        ?OpencastService $opencastService = null,
         RouterInterface $router,
         TranslatorInterface $translator,
         LoggerInterface $logger,