diff --git a/src/Command/MakerCommand.php b/src/Command/MakerCommand.php
index 4bf01cb5c..b81b8dbea 100644
--- a/src/Command/MakerCommand.php
+++ b/src/Command/MakerCommand.php
@@ -32,19 +32,19 @@
  */
 final class MakerCommand extends Command
 {
-    private $fileManager;
     private $maker;
     private $rootNamespace;
+    private $fileManager;
     private $inputConfig;
     /** @var ConsoleStyle */
     private $io;
     private $checkDependencies = true;
 
-    public function __construct(FileManager $fileManager, MakerInterface $maker, string $rootNamespace)
+    public function __construct(MakerInterface $maker, string $rootNamespace, FileManager $fileManager)
     {
-        $this->fileManager = $fileManager;
         $this->maker = $maker;
         $this->rootNamespace = trim($rootNamespace, '\\');
+        $this->fileManager = $fileManager;
         $this->inputConfig = new InputConfiguration();
 
         parent::__construct();
@@ -90,6 +90,16 @@ protected function interact(InputInterface $input, OutputInterface $output)
 
     protected function execute(InputInterface $input, OutputInterface $output)
     {
+        if (!$this->fileManager->isNamespaceConfiguredToAutoload($this->rootNamespace)) {
+            throw new \LogicException(
+                sprintf(
+                    'It looks like your app may be using a namespace other than "%s".'.
+                    ' See https://symfony.com/doc/current/bundles/SymfonyMakerBundle/index.html for how to configure this.',
+                    $this->rootNamespace
+                )
+            );
+        }
+
         $generator = new Generator($this->fileManager, $this->rootNamespace);
 
         $this->maker->generate($input, $this->io, $generator);
diff --git a/src/DependencyInjection/CompilerPass/MakeCommandRegistrationPass.php b/src/DependencyInjection/CompilerPass/MakeCommandRegistrationPass.php
index bc0024fb2..93e936e74 100644
--- a/src/DependencyInjection/CompilerPass/MakeCommandRegistrationPass.php
+++ b/src/DependencyInjection/CompilerPass/MakeCommandRegistrationPass.php
@@ -35,7 +35,7 @@ public function process(ContainerBuilder $container)
 
             $commandDefinition = new ChildDefinition('maker.auto_command.abstract');
             $commandDefinition->setClass(MakerCommand::class);
-            $commandDefinition->replaceArgument(1, new Reference($id));
+            $commandDefinition->replaceArgument(0, new Reference($id));
             $commandDefinition->addTag('console.command', ['command' => $class::getCommandName()]);
 
             $container->setDefinition(sprintf('maker.auto_command.%s', Str::asTwigVariable($class::getCommandName())), $commandDefinition);
diff --git a/src/DependencyInjection/MakerExtension.php b/src/DependencyInjection/MakerExtension.php
index 906e8ee7c..d9fbc73cf 100644
--- a/src/DependencyInjection/MakerExtension.php
+++ b/src/DependencyInjection/MakerExtension.php
@@ -40,7 +40,7 @@ public function load(array $configs, ContainerBuilder $container)
         $rootNamespace = trim($config['root_namespace'], '\\');
 
         $makeCommandDefinition = $container->getDefinition('maker.auto_command.abstract');
-        $makeCommandDefinition->replaceArgument(2, $rootNamespace);
+        $makeCommandDefinition->replaceArgument(1, $rootNamespace);
 
         $doctrineHelperDefinition = $container->getDefinition('maker.doctrine_helper');
         $doctrineHelperDefinition->replaceArgument(0, $rootNamespace.'\\Entity');
diff --git a/src/FileManager.php b/src/FileManager.php
index 60a30ed0a..386abe1b3 100644
--- a/src/FileManager.php
+++ b/src/FileManager.php
@@ -163,6 +163,11 @@ public function getNamespacePrefixForClass(string $className): string
         return $this->autoloaderUtil->getNamespacePrefixForClass($className);
     }
 
+    public function isNamespaceConfiguredToAutoload(string $namespace): string
+    {
+        return $this->autoloaderUtil->isNamespaceConfiguredToAutoload($namespace);
+    }
+
     /**
      * Resolve '../' in paths (like real_path), but for non-existent files.
      *
diff --git a/src/Resources/config/services.xml b/src/Resources/config/services.xml
index e60dbe9c8..5f29ef56b 100644
--- a/src/Resources/config/services.xml
+++ b/src/Resources/config/services.xml
@@ -33,9 +33,9 @@
             </service>
 
             <service id="maker.auto_command.abstract" class="Symfony\Bundle\MakerBundle\Command\MakerCommand" abstract="true">
-                <argument type="service" id="maker.file_manager" />
                 <argument /> <!-- maker -->
                 <argument /> <!-- root namespace -->
+                <argument type="service" id="maker.file_manager" />
             </service>
         </services>
 </container>
diff --git a/tests/Command/MakerCommandTest.php b/tests/Command/MakerCommandTest.php
index 09bac5e34..f1a078ea4 100644
--- a/tests/Command/MakerCommandTest.php
+++ b/tests/Command/MakerCommandTest.php
@@ -26,7 +26,24 @@ public function testExceptionOnMissingDependencies()
 
         $fileManager = $this->createMock(FileManager::class);
 
-        $command = new MakerCommand($fileManager, $maker, 'App\\');
+        $command = new MakerCommand($maker, 'App', $fileManager);
+        // needed because it's normally set by the Application
+        $command->setName('make:foo');
+        $tester = new CommandTester($command);
+        $tester->execute(array());
+    }
+
+    /**
+     * @expectedException \LogicException
+     * @expectedExceptionMessage using a namespace other than "Unknown".
+     */
+    public function testExceptionOnUnknownRootNamespace()
+    {
+        $maker = $this->createMock(MakerInterface::class);
+
+        $fileManager = $this->createMock(FileManager::class);
+
+        $command = new MakerCommand($maker, 'Unknown', $fileManager);
         // needed because it's normally set by the Application
         $command->setName('make:foo');
         $tester = new CommandTester($command);