diff --git a/fractor/composer.json b/fractor/composer.json
index f1b7727c..724be146 100644
--- a/fractor/composer.json
+++ b/fractor/composer.json
@@ -17,7 +17,8 @@
         "symfony/console": "^6.4",
         "symfony/dependency-injection": "^6.4",
         "symfony/filesystem": "^6.4",
-        "symfony/finder": "^6.4"
+        "symfony/finder": "^6.4",
+        "webmozart/assert": "^1.11"
     },
     "require-dev": {
         "ergebnis/composer-normalize": "^2.42",
diff --git a/fractor/config/application.php b/fractor/config/application.php
index a9c61427..32d8d001 100644
--- a/fractor/config/application.php
+++ b/fractor/config/application.php
@@ -15,7 +15,7 @@
 
 return static function (ContainerConfigurator $containerConfigurator, ContainerBuilder $containerBuilder): void {
     $parameters = $containerConfigurator->parameters();
-    $parameters->set(Option::PATHS, []);
+    $parameters->set(Option::PATHS, [__DIR__]);
     $services = $containerConfigurator->services();
     $services->defaults()
         ->autowire()
diff --git a/fractor/src/Fractor/FractorRunner.php b/fractor/src/Fractor/FractorRunner.php
index 21a50a39..71a8799b 100644
--- a/fractor/src/Fractor/FractorRunner.php
+++ b/fractor/src/Fractor/FractorRunner.php
@@ -26,10 +26,6 @@ public function __construct(private FileFinder $fileFinder, private FileCollecto
 
     public function run(Output $output, bool $dryRun = false): void
     {
-        if ($this->configuration->getPaths() === []) {
-            throw new \RuntimeException('No directories given');
-        }
-
         $files = $this->fileFinder->findFiles($this->configuration->getPaths(), $this->configuration->getFileExtensions());
 
         $output->progressStart(count($files));
diff --git a/fractor/src/ValueObject/Configuration.php b/fractor/src/ValueObject/Configuration.php
index 8b0e1278..faf1bc11 100644
--- a/fractor/src/ValueObject/Configuration.php
+++ b/fractor/src/ValueObject/Configuration.php
@@ -4,6 +4,8 @@
 
 namespace a9f\Fractor\ValueObject;
 
+use Webmozart\Assert\Assert;
+
 final readonly class Configuration
 {
     /**
@@ -12,6 +14,8 @@
      */
     public function __construct(private array $fileExtensions, private array $paths)
     {
+        Assert::notEmpty($this->paths, 'No directories given');
+        Assert::allStringNotEmpty($this->paths, 'No directories given');
     }
 
     /**