diff --git a/README.md b/README.md
index 68f9cb8..11d1c8b 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,32 @@ return [
 ];
 ```
 
+### 3. Configure NelmioApiDocBundle
+
+This bundle reads its routes from NelmioApiDocBundle's areas, so Nelmio must be **registered and
+configured** — installing it via Composer is not enough. Its Flex recipe normally does this, but if
+the recipe was skipped you have to do it by hand. Add it to `config/bundles.php`:
+
+```php
+return [
+    // ...
+    Nelmio\ApiDocBundle\NelmioApiDocBundle::class => ['all' => true],
+];
+```
+
+And define at least one area in `config/packages/nelmio_api_doc.yaml`:
+
+```yaml
+nelmio_api_doc:
+    areas:
+        default:
+            path_patterns: ['^/api']
+```
+
+Without this, the container fails to compile and `cache:clear` reports which part
+is missing — the `config/bundles.php` entry or the package config — along with
+the configuration to add.
+
 ## Usage
 
 ### 1. Create a Command DTO
@@ -161,6 +187,7 @@ See [Extension Points](docs/extension-points.md) for a worked example of each ex
 
 - PHP 8.4+
 - Symfony 7.3+ or 8.0+
+- NelmioApiDocBundle 5.8+, registered and configured with at least one area
 
 ## License
 
diff --git a/src/DependencyInjection/Compiler/CollectNelmioApiDocRoutesPass.php b/src/DependencyInjection/Compiler/CollectNelmioApiDocRoutesPass.php
index a7fbf79..963d1e9 100644
--- a/src/DependencyInjection/Compiler/CollectNelmioApiDocRoutesPass.php
+++ b/src/DependencyInjection/Compiler/CollectNelmioApiDocRoutesPass.php
@@ -16,6 +16,7 @@
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Definition;
+use Symfony\Component\DependencyInjection\Exception\LogicException;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\ServiceLocator;
 
@@ -27,7 +28,7 @@ final class CollectNelmioApiDocRoutesPass implements CompilerPassInterface
     public function process(ContainerBuilder $container): void
     {
         if (!$container->hasParameter('nelmio_api_doc.areas')) {
-            return;
+            throw new LogicException($this->missingNelmioMessage($container));
         }
 
         /** @var list<string> $areas */
@@ -54,6 +55,29 @@ public function process(ContainerBuilder $container): void
         $container->setParameter('stixx_openapi_command.nelmio.path_patterns', $pathPatterns);
     }
 
+    /**
+     * Without the areas parameter the routes locator is never registered, and config/routing.php fails with
+     * an opaque "service does not exist" error. Name the missing half of the setup instead.
+     */
+    private function missingNelmioMessage(ContainerBuilder $container): string
+    {
+        $example = "\n\nnelmio_api_doc:\n"
+            ."    areas:\n"
+            ."        default:\n"
+            ."            path_patterns: ['^/api']\n";
+
+        if ($container->hasExtension('nelmio_api_doc')) {
+            return 'NelmioApiDocBundle is registered but has no configuration, so it defined no areas. '
+                .'StixxOpenApiCommandBundle needs at least one area. Create config/packages/nelmio_api_doc.yaml '
+                .'with, for example:'.$example;
+        }
+
+        return 'NelmioApiDocBundle is not registered in config/bundles.php (its Flex recipe may have been '
+            .'skipped). StixxOpenApiCommandBundle requires it to be both registered and configured. Add '
+            .'"Nelmio\ApiDocBundle\NelmioApiDocBundle::class => [\'all\' => true]" to config/bundles.php, then '
+            .'create config/packages/nelmio_api_doc.yaml with at least one area, for example:'.$example;
+    }
+
     /**
      * Reads `path_patterns` from the FilteredRouteCollectionBuilder factory definition that Nelmio
      * registers per area. When the area has no filter config, Nelmio uses the full router collection
diff --git a/tests/Functional/App/MissingNelmioKernel.php b/tests/Functional/App/MissingNelmioKernel.php
new file mode 100644
index 0000000..a99b60e
--- /dev/null
+++ b/tests/Functional/App/MissingNelmioKernel.php
@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the StixxOpenApiCommandBundle package.
+ *
+ * (c) Stixx
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Stixx\OpenApiCommandBundle\Tests\Functional\App;
+
+use Nyholm\BundleTest\TestKernel;
+use Stixx\OpenApiCommandBundle\StixxOpenApiCommandBundle;
+use Symfony\Bundle\FrameworkBundle\FrameworkBundle;
+
+/**
+ * A kernel without NelmioApiDocBundle, reproducing a skipped Flex recipe.
+ */
+class MissingNelmioKernel extends TestKernel
+{
+    public function __construct(string $environment, bool $debug)
+    {
+        parent::__construct($environment, $debug);
+
+        $this->addTestBundle(FrameworkBundle::class);
+        // NelmioApiDocBundle is deliberately not registered.
+        $this->addTestBundle(StixxOpenApiCommandBundle::class);
+        $this->addTestConfig(__DIR__.'/../Resources/config/without_nelmio.php');
+    }
+
+    public function getProjectDir(): string
+    {
+        return __DIR__.'/../';
+    }
+}
diff --git a/tests/Functional/MissingNelmioConfigurationTest.php b/tests/Functional/MissingNelmioConfigurationTest.php
new file mode 100644
index 0000000..d5b9ff3
--- /dev/null
+++ b/tests/Functional/MissingNelmioConfigurationTest.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the StixxOpenApiCommandBundle package.
+ *
+ * (c) Stixx
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Stixx\OpenApiCommandBundle\Tests\Functional;
+
+use PHPUnit\Framework\Attributes\WithoutErrorHandler;
+use Stixx\OpenApiCommandBundle\Tests\Functional\App\MissingNelmioKernel;
+use Symfony\Component\DependencyInjection\Exception\LogicException;
+
+/**
+ * The unit tests call the compiler pass directly, which cannot show whether the exception survives a real
+ * container build — the bundle's own prepend() also writes nelmio_api_doc config, so something upstream
+ * could fail first with a different error and the pass would never run.
+ */
+final class MissingNelmioConfigurationTest extends AbstractKernelTestCase
+{
+    #[WithoutErrorHandler]
+    public function testBootingWithoutNelmioApiDocBundleExplainsHowToFixIt(): void
+    {
+        // Arrange
+        $kernel = new MissingNelmioKernel('test', true);
+
+        // Assert
+        $this->expectException(LogicException::class);
+        $this->expectExceptionMessage('NelmioApiDocBundle is not registered in config/bundles.php');
+
+        // Act
+        $kernel->boot();
+    }
+}
diff --git a/tests/Functional/Resources/config/without_nelmio.php b/tests/Functional/Resources/config/without_nelmio.php
new file mode 100644
index 0000000..673d56b
--- /dev/null
+++ b/tests/Functional/Resources/config/without_nelmio.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the StixxOpenApiCommandBundle package.
+ *
+ * (c) Stixx
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
+
+return static function (ContainerConfigurator $container): void {
+    $container->extension('framework', [
+        'test' => true,
+        'messenger' => [
+            'enabled' => true,
+        ],
+        'serializer' => [
+            'enabled' => true,
+        ],
+        'validation' => [
+            'enabled' => true,
+        ],
+        'http_method_override' => false,
+        'php_errors' => [
+            'log' => false,
+        ],
+    ]);
+};
diff --git a/tests/Unit/DependencyInjection/Compiler/CollectNelmioApiDocRoutesPassTest.php b/tests/Unit/DependencyInjection/Compiler/CollectNelmioApiDocRoutesPassTest.php
index f22ee22..9582b8d 100644
--- a/tests/Unit/DependencyInjection/Compiler/CollectNelmioApiDocRoutesPassTest.php
+++ b/tests/Unit/DependencyInjection/Compiler/CollectNelmioApiDocRoutesPassTest.php
@@ -13,12 +13,15 @@
 
 namespace Stixx\OpenApiCommandBundle\Tests\Unit\DependencyInjection\Compiler;
 
+use Nelmio\ApiDocBundle\DependencyInjection\NelmioApiDocExtension;
 use Nelmio\ApiDocBundle\Routing\FilteredRouteCollectionBuilder;
+use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 use stdClass;
 use Stixx\OpenApiCommandBundle\DependencyInjection\Compiler\CollectNelmioApiDocRoutesPass;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Definition;
+use Symfony\Component\DependencyInjection\Exception\LogicException;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\ServiceLocator;
 use Symfony\Component\Routing\RouteCollection;
@@ -60,18 +63,65 @@ public function testProcessWithAreas(): void
         );
     }
 
-    public function testProcessWithoutParameter(): void
+    /**
+     * @param list<string> $expected
+     * @param list<string> $notExpected
+     */
+    #[DataProvider('missingSetupProvider')]
+    public function testProcessFailsWhenNelmioIsNotConfigured(bool $registered, array $expected, array $notExpected): void
     {
-        // Arrange
+        // Arrange — a registered bundle has an extension; without config it still sets no areas parameter.
         $container = new ContainerBuilder();
-        $pass = new CollectNelmioApiDocRoutesPass();
+        if ($registered) {
+            $container->registerExtension(new NelmioApiDocExtension());
+        }
 
         // Act
-        $pass->process($container);
+        $message = null;
+
+        try {
+            (new CollectNelmioApiDocRoutesPass())->process($container);
+        } catch (LogicException $exception) {
+            $message = $exception->getMessage();
+        }
 
         // Assert
-        self::assertFalse($container->hasDefinition('stixx_openapi_command.nelmio.routes_locator'));
-        self::assertFalse($container->hasParameter('stixx_openapi_command.nelmio.path_patterns'));
+        self::assertNotNull($message, 'Expected a LogicException when nelmio_api_doc.areas is missing.');
+
+        foreach ($expected as $needle) {
+            self::assertStringContainsString($needle, $message);
+        }
+
+        foreach ($notExpected as $needle) {
+            self::assertStringNotContainsString($needle, $message);
+        }
+    }
+
+    /**
+     * @return iterable<string, array{bool, list<string>, list<string>}>
+     */
+    public static function missingSetupProvider(): iterable
+    {
+        yield 'bundle not registered' => [
+            false,
+            [
+                'NelmioApiDocBundle is not registered in config/bundles.php',
+                'NelmioApiDocBundle::class',
+                'config/packages/nelmio_api_doc.yaml',
+                "path_patterns: ['^/api']",
+            ],
+            [],
+        ];
+
+        // Already registered, so the message must not ask for a config/bundles.php entry.
+        yield 'bundle registered without config' => [
+            true,
+            [
+                'NelmioApiDocBundle is registered but has no configuration',
+                'config/packages/nelmio_api_doc.yaml',
+            ],
+            ['config/bundles.php'],
+        ];
     }
 
     public function testExtractsPathPatternsFromFilteredRouteCollectionBuilderFactory(): void