diff --git a/lib/AutomaticEmails/WooCommerce/Events/PurchasedInCategory.php b/lib/AutomaticEmails/WooCommerce/Events/PurchasedInCategory.php
index b48c601ab7..66f7a12761 100644
--- a/lib/AutomaticEmails/WooCommerce/Events/PurchasedInCategory.php
+++ b/lib/AutomaticEmails/WooCommerce/Events/PurchasedInCategory.php
@@ -110,7 +110,7 @@ class PurchasedInCategory {
     $ordered_product_categories = [];
     foreach ($order_details->get_items() as $order_item_product) {
       $product = $order_item_product->get_product();
-      if (!$product || !is_callable([$product, 'get_category_ids'])) {
+      if (!$product instanceof \WC_Product) {
         continue;
       }
       $ordered_product_categories = array_merge($ordered_product_categories, $product->get_category_ids());
diff --git a/lib/AutomaticEmails/WooCommerce/Events/PurchasedProduct.php b/lib/AutomaticEmails/WooCommerce/Events/PurchasedProduct.php
index a5a0d51287..57e4c66840 100644
--- a/lib/AutomaticEmails/WooCommerce/Events/PurchasedProduct.php
+++ b/lib/AutomaticEmails/WooCommerce/Events/PurchasedProduct.php
@@ -118,7 +118,7 @@ class PurchasedProduct {
     }
 
     $ordered_products = array_map(function($product) {
-      return is_callable([$product, 'get_product_id']) ? $product->get_product_id() : null;
+      return ($product instanceof \WC_Order_Item_Product) ? $product->get_product_id() : null;
     }, $order_details->get_items());
     $ordered_products = array_values(array_filter($ordered_products));
 
diff --git a/tasks/code_sniffer/MailPoet/ruleset.xml b/tasks/code_sniffer/MailPoet/ruleset.xml
index 756a04a71d..95a79c17bc 100644
--- a/tasks/code_sniffer/MailPoet/ruleset.xml
+++ b/tasks/code_sniffer/MailPoet/ruleset.xml
@@ -2,7 +2,7 @@
 <ruleset name="MailPoet">
   <config name="installed_paths" value="tasks/code_sniffer/vendor/squizlabs/php_codesniffer,tasks/code_sniffer/vendor/phpcompatibility/php-compatibility,tasks/code_sniffer/vendor/slevomat/coding-standard"/>
   <description>MailPoet specific rule set</description>
-
+  <exclude-pattern>*/phpstan/woocommerce.php</exclude-pattern>
   <!-- Namespaces -->
   <rule ref="PSR2.Namespaces.NamespaceDeclaration"/>
   <rule ref="SlevomatCodingStandard.Namespaces.NamespaceDeclaration"/>
diff --git a/tasks/phpstan/woocommerce.php b/tasks/phpstan/woocommerce.php
index 2bce61e5f5..99019aeeae 100644
--- a/tasks/phpstan/woocommerce.php
+++ b/tasks/phpstan/woocommerce.php
@@ -64,3 +64,15 @@ class WC_DateTime extends \DateTime {
 */
 class WC_Order { // phpcs:ignore
 }
+
+/**
+ * @method int get_product_id(string $context = 'view')
+ */
+class WC_Order_Item_Product { // phpcs:ignore
+}
+
+/**
+ * @method int[] get_category_ids(string $context = 'view')
+ */
+class WC_Product { // phpcs:ignore
+}
diff --git a/tests/integration/AutomaticEmails/WooCommerce/Events/PurchasedProductTest.php b/tests/integration/AutomaticEmails/WooCommerce/Events/PurchasedProductTest.php
index 3ef900a8bd..47c841f841 100644
--- a/tests/integration/AutomaticEmails/WooCommerce/Events/PurchasedProductTest.php
+++ b/tests/integration/AutomaticEmails/WooCommerce/Events/PurchasedProductTest.php
@@ -221,13 +221,13 @@ class PurchasedProductTest extends \MailPoetTest {
         'get_items' => function() use ($incorrect_product_id, $product_id) {
           return [
             Stub::make(
-              new ItemDetails(),
+              \WC_Order_Item_Product::class,
               [
                 'get_product_id' => $incorrect_product_id,
               ]
             ),
             Stub::make(
-              new ItemDetails(),
+              \WC_Order_Item_Product::class,
               [
                 'get_product_id' => $product_id,
               ]
diff --git a/tests/integration/_bootstrap.php b/tests/integration/_bootstrap.php
index 04c48923ee..0f91f8b46d 100644
--- a/tests/integration/_bootstrap.php
+++ b/tests/integration/_bootstrap.php
@@ -231,6 +231,10 @@ if (!function_exists('WC')) {
   function WC() {
     return new WooCommerce;
   }
+  class WC_Order_Item_Product { // phpcs:ignore
+    function get_product_id() { // phpcs:ignore
+    }
+  }
 }
 
 include '_fixtures.php';