diff --git a/composer.json b/composer.json
index 5c5528a..c708488 100644
--- a/composer.json
+++ b/composer.json
@@ -56,6 +56,7 @@
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^3.47.1",
+        "league/container": "^4.2",
         "phpstan/phpstan": "^1.10",
         "phpunit/phpunit": "^10.0",
         "symfony/yaml": "^6.0|^7.0",
diff --git a/src/Adapters/Slim/OpenApiResponseVerifier.php b/src/Adapters/Slim/OpenApiResponseVerifier.php
index c77c392..ed83570 100644
--- a/src/Adapters/Slim/OpenApiResponseVerifier.php
+++ b/src/Adapters/Slim/OpenApiResponseVerifier.php
@@ -25,6 +25,8 @@ public function registerOpenApiVerifier(?App $app, ?string $specification = null
                 $container[OpenApiVerifierMiddleware::OPENAPI_VERFIER_CONTAINER_KEY] = $this;
             } elseif (method_exists($container, 'set')) {
                 $container->set(OpenApiVerifierMiddleware::OPENAPI_VERFIER_CONTAINER_KEY, $this);
+            } elseif (method_exists($container, 'add')) {
+                $container->add(OpenApiVerifierMiddleware::OPENAPI_VERFIER_CONTAINER_KEY, $this);
             } else {
                 throw new \RuntimeException('Unusable container');
             }
diff --git a/tests/Adapters/SlimAdapterTest.php b/tests/Adapters/SlimAdapterTest.php
index 5d65625..5ccf97a 100644
--- a/tests/Adapters/SlimAdapterTest.php
+++ b/tests/Adapters/SlimAdapterTest.php
@@ -2,11 +2,11 @@
 
 namespace Radebatz\OpenApi\Verifier\Tests\Adapters;
 
+use League\Container\Container;
 use Nyholm\Psr7\Factory\Psr17Factory;
 use PHPUnit\Framework\AssertionFailedError;
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
-use Psr\Container\ContainerInterface;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
 use Radebatz\OpenApi\Verifier\Adapters\Slim\OpenApiResponseVerifier;
@@ -62,7 +62,7 @@ protected function runApp(string $requestMethod, string $requestUri, bool $valid
     {
         $request = (new Psr17Factory())->createServerRequest($requestMethod, $requestUri);
 
-        $app = AppFactory::create(container: $this->container());
+        $app = AppFactory::create(container: new Container());
 
         // register test route as we do not have an actual app...
         if ($valid) {
@@ -95,26 +95,4 @@ protected function runApp(string $requestMethod, string $requestUri, bool $valid
 
         return $app->handle($request);
     }
-
-    protected function container(): ContainerInterface
-    {
-        return new class() implements ContainerInterface {
-            protected $container = [];
-
-            public function get(string $id)
-            {
-                return $this->container[$id] ?? null;
-            }
-
-            public function has(string $id)
-            {
-                return array_key_exists($id, $this->container);
-            }
-
-            public function set(string $id, $value)
-            {
-                $this->container[$id] = $value;
-            }
-        };
-    }
 }