diff --git a/.php_cs.dist b/.php_cs.dist
index dd93021c..b890baa4 100644
--- a/.php_cs.dist
+++ b/.php_cs.dist
@@ -32,6 +32,7 @@ $rules = [
     'no_superfluous_phpdoc_tags' => ['allow_mixed' => true],
     'no_useless_else' => true,
     'no_useless_return' => true,
+    'nullable_type_declaration_for_default_null_value' => ['use_nullable_type_declaration' => true],
     'ordered_class_elements' => true,
     'ordered_imports' => true,
     'phpdoc_order' => true,
diff --git a/src/Block/TreeBlockService.php b/src/Block/TreeBlockService.php
index 4d08f768..6b231880 100644
--- a/src/Block/TreeBlockService.php
+++ b/src/Block/TreeBlockService.php
@@ -51,7 +51,7 @@ public function buildEditForm(FormMapper $form, BlockInterface $block): void
     /**
      * {@inheritdoc}
      */
-    public function execute(BlockContextInterface $blockContext, Response $response = null)
+    public function execute(BlockContextInterface $blockContext, ?Response $response = null)
     {
         return $this->renderResponse($blockContext->getTemplate(), [
             'block' => $blockContext->getBlock(),
diff --git a/src/Datagrid/ProxyQuery.php b/src/Datagrid/ProxyQuery.php
index 9d8728c4..caa6e31b 100644
--- a/src/Datagrid/ProxyQuery.php
+++ b/src/Datagrid/ProxyQuery.php
@@ -61,7 +61,7 @@ class ProxyQuery implements ProxyQueryInterface
     /**
      * PHPCR ODM Document Manager.
      *
-     * @var DocumentManager;
+     * @var DocumentManager
      */
     protected $documentManager;