diff --git a/features/configuration/autodiscovering_application_kernel.feature b/features/configuration/autodiscovering_application_kernel.feature
new file mode 100644
index 0000000..30cb9eb
--- /dev/null
+++ b/features/configuration/autodiscovering_application_kernel.feature
@@ -0,0 +1,214 @@
+Feature: Autodiscovering the application kernel
+
+    Background:
+        Given a standard Symfony autoloader configured
+        And a feature file containing:
+        """
+        Feature:
+            Scenario:
+                Then the passed service should be an instance of "\Psr\Container\ContainerInterface"
+        """
+        And a Behat configuration containing:
+        """
+        default:
+            extensions:
+                FriendsOfBehat\SymfonyExtension: ~
+
+            suites:
+                default:
+                    contexts:
+                        - App\Tests\SomeContext
+        """
+        And a context file "tests/SomeContext.php" containing:
+        """
+        <?php
+
+        namespace App\Tests;
+
+        use Behat\Behat\Context\Context;
+
+        final class SomeContext implements Context {
+            private $service;
+
+            public function __construct($service = null) { $this->service = $service; }
+
+            /** @Then the passed service should be an instance of :expected */
+            public function serviceShouldBe(string $expected): void
+            {
+                assert(is_object($this->service));
+                assert($this->service instanceof $expected);
+            }
+        }
+        """
+        And a services file "config/services.yaml" containing:
+        """
+        services:
+            App\Tests\SomeContext:
+                public: true
+                arguments:
+                    - "@service_container"
+        """
+
+    Scenario: Autodiscovering kernel in Symfony 3 directory structure application
+        Given a kernel file "src/Kernel.php" containing:
+        """
+        <?php
+
+        namespace App;
+
+        use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
+        use Symfony\Component\Config\Loader\LoaderInterface;
+        use Symfony\Component\DependencyInjection\ContainerBuilder;
+        use Symfony\Component\HttpFoundation\Response;
+        use Symfony\Component\HttpKernel\Kernel as HttpKernel;
+        use Symfony\Component\Routing\RouteCollectionBuilder;
+
+        class Kernel extends HttpKernel
+        {
+            use MicroKernelTrait;
+
+            public function registerBundles(): iterable
+            {
+                return [
+                    new \Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
+                    new \FriendsOfBehat\SymfonyExtension\Bundle\FriendsOfBehatSymfonyExtensionBundle(),
+                ];
+            }
+
+            protected function configureContainer(ContainerBuilder $container, LoaderInterface $loader): void
+            {
+                $container->loadFromExtension('framework', [
+                    'test' => $this->getEnvironment() === 'test',
+                    'secret' => 'Pigeon',
+                ]);
+
+                $loader->load(__DIR__ . '/../config/services.yaml');
+            }
+
+            protected function configureRoutes(RouteCollectionBuilder $routes): void {}
+        }
+        """
+        When I run Behat
+        Then it should pass
+
+    Scenario: Autodiscovering kernel in Symfony 4 directory structure application
+        Given a kernel file "app/AppKernel.php" containing:
+        """
+        <?php
+
+        use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
+        use Symfony\Component\Config\Loader\LoaderInterface;
+        use Symfony\Component\DependencyInjection\ContainerBuilder;
+        use Symfony\Component\HttpFoundation\Response;
+        use Symfony\Component\HttpKernel\Kernel as HttpKernel;
+        use Symfony\Component\Routing\RouteCollectionBuilder;
+
+        class AppKernel extends HttpKernel
+        {
+            use MicroKernelTrait;
+
+            public function registerBundles(): iterable
+            {
+                return [
+                    new \Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
+                    new \FriendsOfBehat\SymfonyExtension\Bundle\FriendsOfBehatSymfonyExtensionBundle(),
+                ];
+            }
+
+            protected function configureContainer(ContainerBuilder $container, LoaderInterface $loader): void
+            {
+                $container->loadFromExtension('framework', [
+                    'test' => $this->getEnvironment() === 'test',
+                    'secret' => 'Pigeon',
+                ]);
+
+                $loader->load(__DIR__ . '/../config/services.yaml');
+            }
+
+            protected function configureRoutes(RouteCollectionBuilder $routes): void {}
+        }
+        """
+        When I run Behat
+        Then it should pass
+
+    Scenario: Failing to autodiscover the kernel
+        When I run Behat
+        Then it should fail with "Could not autodiscover the application kernel"
+
+    Scenario: Failing to autodiscover the kernel
+        Given a kernel file "src/Kernel.php" containing:
+        """
+        <?php
+
+        namespace App;
+
+        use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
+        use Symfony\Component\Config\Loader\LoaderInterface;
+        use Symfony\Component\DependencyInjection\ContainerBuilder;
+        use Symfony\Component\HttpFoundation\Response;
+        use Symfony\Component\HttpKernel\Kernel as HttpKernel;
+        use Symfony\Component\Routing\RouteCollectionBuilder;
+
+        class Kernel extends HttpKernel
+        {
+            use MicroKernelTrait;
+
+            public function registerBundles(): iterable
+            {
+                return [
+                    new \Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
+                    new \FriendsOfBehat\SymfonyExtension\Bundle\FriendsOfBehatSymfonyExtensionBundle(),
+                ];
+            }
+
+            protected function configureContainer(ContainerBuilder $container, LoaderInterface $loader): void
+            {
+                $container->loadFromExtension('framework', [
+                    'test' => $this->getEnvironment() === 'test',
+                    'secret' => 'Pigeon',
+                ]);
+
+                $loader->load(__DIR__ . '/../config/services.yaml');
+            }
+
+            protected function configureRoutes(RouteCollectionBuilder $routes): void {}
+        }
+        """
+        And a kernel file "app/AppKernel.php" containing:
+        """
+        <?php
+
+        use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
+        use Symfony\Component\Config\Loader\LoaderInterface;
+        use Symfony\Component\DependencyInjection\ContainerBuilder;
+        use Symfony\Component\HttpFoundation\Response;
+        use Symfony\Component\HttpKernel\Kernel as HttpKernel;
+        use Symfony\Component\Routing\RouteCollectionBuilder;
+
+        class AppKernel extends HttpKernel
+        {
+            use MicroKernelTrait;
+
+            public function registerBundles(): iterable
+            {
+                return [
+                    new \Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
+                    new \FriendsOfBehat\SymfonyExtension\Bundle\FriendsOfBehatSymfonyExtensionBundle(),
+                ];
+            }
+
+            protected function configureContainer(ContainerBuilder $container, LoaderInterface $loader): void
+            {
+                $container->loadFromExtension('framework', [
+                    'test' => $this->getEnvironment() === 'test',
+                    'secret' => 'Pigeon',
+                ]);
+
+                $loader->load(__DIR__ . '/../config/services.yaml');
+            }
+
+            protected function configureRoutes(RouteCollectionBuilder $routes): void {}
+        }
+        """
+        When I run Behat
+        Then it should fail with "Could not autodiscover the application kernel"
diff --git a/features/configuration/loading_kernel_based_on_configurtion.feature b/features/configuration/loading_configured_application_kernel.feature
similarity index 99%
rename from features/configuration/loading_kernel_based_on_configurtion.feature
rename to features/configuration/loading_configured_application_kernel.feature
index 8efc077..69f0e02 100644
--- a/features/configuration/loading_kernel_based_on_configurtion.feature
+++ b/features/configuration/loading_configured_application_kernel.feature
@@ -1,4 +1,4 @@
-Feature: Loading kernel based on configuration
+Feature: Loading configured application kernel
 
     Background:
         Given a standard Symfony autoloader configured
diff --git a/src/ServiceContainer/SymfonyExtension.php b/src/ServiceContainer/SymfonyExtension.php
index bc6140b..b96a5bb 100644
--- a/src/ServiceContainer/SymfonyExtension.php
+++ b/src/ServiceContainer/SymfonyExtension.php
@@ -56,7 +56,7 @@ final class SymfonyExtension implements Extension
                     ->addDefaultsIfNotSet()
                     ->children()
                         ->scalarNode('path')->defaultNull()->end()
-                        ->scalarNode('class')->isRequired()->end()
+                        ->scalarNode('class')->defaultNull()->end()
                     ->end()
                 ->end()
             ->end()
@@ -65,7 +65,7 @@ final class SymfonyExtension implements Extension
 
     public function load(ContainerBuilder $container, array $config): void
     {
-        $this->loadKernel($container, $config['kernel']);
+        $this->loadKernel($container, $this->processKernelConfiguration($config['kernel']));
         $this->loadDriverKernel($container);
 
         $this->loadKernelRebooter($container);
@@ -154,4 +154,35 @@ final class SymfonyExtension implements Extension
 
         $container->setDefinition('fob_symfony.mink.parameters', $minkParametersDefinition);
     }
+
+    private function processKernelConfiguration(array $config): array
+    {
+        if ($config['class'] !== null) {
+            return $config;
+        }
+
+        $autoconfigured = 0;
+
+        if (class_exists('\App\Kernel')) {
+            $config['class'] = '\App\Kernel';
+
+            ++$autoconfigured;
+        }
+
+        if (file_exists('app/AppKernel.php')) {
+            $config['class'] = '\AppKernel';
+            $config['path'] = 'app/AppKernel.php';
+
+            ++$autoconfigured;
+        }
+
+        if ($autoconfigured !== 1) {
+            throw new \RuntimeException(
+                'Could not autodiscover the application kernel. ' .
+                'Please define it manually with "FriendsOfBehat\SymfonyExtension.kernel" configuration option.'
+            );
+        }
+
+        return $config;
+    }
 }