diff --git a/Block/Product/RatingSnippet.php b/Block/Product/RatingSnippet.php
index c6227aa..5984513 100644
--- a/Block/Product/RatingSnippet.php
+++ b/Block/Product/RatingSnippet.php
@@ -39,10 +39,10 @@ public function __construct(
         \Magento\Catalog\Api\CategoryRepositoryInterface $categoryRepository,
         \Magento\Framework\Url\Helper\Data $urlHelper,
         array $data = [],
-        \Magento\Customer\Model\Session $customerSession = null,
-        \Magento\Catalog\Model\CategoryFactory $categoryFactory = null,
-        ReviewsConfig $reviewsConfigHelper = null,
-        StoreManagerInterface $storeManager = null
+        ?\Magento\Customer\Model\Session $customerSession = null,
+        ?\Magento\Catalog\Model\CategoryFactory $categoryFactory = null,
+        ?ReviewsConfig $reviewsConfigHelper = null,
+        ?StoreManagerInterface $storeManager = null
     ) {
         $this->_customerSession = $customerSession;
         $this->categoryFactory = $categoryFactory;
diff --git a/Block/Richsnippet.php b/Block/Richsnippet.php
index 008e214..2dd9067 100755
--- a/Block/Richsnippet.php
+++ b/Block/Richsnippet.php
@@ -85,7 +85,7 @@ public function getRichSnippetSource()
         return '<script src="' . $url . '"></script>';
     }
 
-    public function getRichSnippet($sku = null, $product = null)
+    public function getRichSnippet(?$sku = null, ?$product = null)
     {
         if (isset($sku) && is_array($sku)) {
             $sku = implode(';', $sku);
diff --git a/Model/Api.php b/Model/Api.php
index dee0a0e..6d59409 100755
--- a/Model/Api.php
+++ b/Model/Api.php
@@ -25,7 +25,7 @@ public function __construct(
         $this->store = $storeManagerInterface->getStore();
     }
 
-    public function apiPost($url, $data, $magento_store_id = null)
+    public function apiPost($url, $data, ?$magento_store_id = null)
     {
         if ($magento_store_id == null) {
             $magento_store_id = $this->store->getId();
@@ -51,7 +51,7 @@ public function apiPost($url, $data, $magento_store_id = null)
         return $response;
     }
 
-    protected function getApiDomain($magento_store_id = null)
+    protected function getApiDomain(?$magento_store_id = null)
     {
         return $this->configHelper->getRegion($magento_store_id) == 'US' ? 'api.reviews.io' : 'api.reviews.co.uk';
     }