diff --git a/RouteDescriber/RouteMetadataDescriber.php b/RouteDescriber/RouteMetadataDescriber.php
index 5a7baa4..8dc5b3a 100644
--- a/RouteDescriber/RouteMetadataDescriber.php
+++ b/RouteDescriber/RouteMetadataDescriber.php
@@ -73,7 +73,7 @@ final class RouteMetadataDescriber implements RouteDescriberInterface
     private function getRefParams(OA\OpenApi $api, OA\Operation $operation): array
     {
         /** @var OA\Parameter[] $globalParams */
-        $globalParams = OA\UNDEFINED !== $api->components->parameters ? $api->components->parameters : [];
+        $globalParams = OA\UNDEFINED !== $api->components && OA\UNDEFINED !== $api->components->parameters ? $api->components->parameters : [];
         $existingParams = [];
 
         $operationParameters = OA\UNDEFINED !== $operation->parameters ? $operation->parameters : [];
diff --git a/Tests/RouteDescriber/RouteMetadataDescriberTest.php b/Tests/RouteDescriber/RouteMetadataDescriberTest.php
new file mode 100644
index 0000000..d7b5452
--- /dev/null
+++ b/Tests/RouteDescriber/RouteMetadataDescriberTest.php
@@ -0,0 +1,27 @@
+<?php
+
+/*
+ * This file is part of the NelmioApiDocBundle package.
+ *
+ * (c) Nelmio
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Nelmio\ApiDocBundle\Tests\RouteDescriber;
+
+use Nelmio\ApiDocBundle\RouteDescriber\RouteMetadataDescriber;
+use OpenApi\Annotations\OpenApi;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Routing\Route;
+
+class RouteMetadataDescriberTest extends TestCase
+{
+    public function testUndefinedCheck()
+    {
+        $routeDescriber = new RouteMetadataDescriber();
+
+        $this->assertNull($routeDescriber->describe(new OpenApi([]), new Route('foo'), new \ReflectionMethod(__CLASS__, 'testUndefinedCheck')));
+    }
+}