diff --git a/src/DependencyInjection/Compiler/EventListenerPass.php b/src/DependencyInjection/Compiler/EventListenerPass.php
new file mode 100644
index 00000000..41d7c395
--- /dev/null
+++ b/src/DependencyInjection/Compiler/EventListenerPass.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Patchlevel\EventSourcingBundle\DependencyInjection\Compiler;
+
+use Patchlevel\EventSourcing\EventBus\DefaultEventBus;
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Reference;
+
+use function array_keys;
+use function assert;
+use function is_string;
+
+class EventListenerPass implements CompilerPassInterface
+{
+    public function process(ContainerBuilder $container): void
+    {
+        if (!$container->hasDefinition(DefaultEventBus::class)) {
+            return;
+        }
+
+        foreach (array_keys($container->findTaggedServiceIds('event_sourcing.event_listener')) as $id) {
+            assert(is_string($id));
+            $container->getDefinition(DefaultEventBus::class)->addMethodCall('addListener', [new Reference($id)]);
+        }
+    }
+}
diff --git a/src/DependencyInjection/Configuration.php b/src/DependencyInjection/Configuration.php
index 5c88eb16..cb654b59 100644
--- a/src/DependencyInjection/Configuration.php
+++ b/src/DependencyInjection/Configuration.php
@@ -38,8 +38,7 @@ public function getConfigTreeBuilder(): TreeBuilder
             ->end()
 
             ->scalarNode('message_bus')
-            ->isRequired()
-            ->cannotBeEmpty()
+            ->defaultNull()
             ->end()
 
             ->arrayNode('aggregates')
diff --git a/src/DependencyInjection/PatchlevelEventSourcingExtension.php b/src/DependencyInjection/PatchlevelEventSourcingExtension.php
index 441cdf9f..ec254364 100644
--- a/src/DependencyInjection/PatchlevelEventSourcingExtension.php
+++ b/src/DependencyInjection/PatchlevelEventSourcingExtension.php
@@ -24,6 +24,7 @@
 use Patchlevel\EventSourcing\Console\Command\ShowCommand;
 use Patchlevel\EventSourcing\Console\Command\WatchCommand;
 use Patchlevel\EventSourcing\Console\DoctrineHelper;
+use Patchlevel\EventSourcing\EventBus\DefaultEventBus;
 use Patchlevel\EventSourcing\EventBus\EventBus;
 use Patchlevel\EventSourcing\EventBus\Listener;
 use Patchlevel\EventSourcing\EventBus\SymfonyEventBus;
@@ -81,27 +82,42 @@ public function load(array $configs, ContainerBuilder $container): void
     }
 
     /**
-     * @param array{message_bus: string} $config
+     * @param array{message_bus: ?string} $config
      */
     private function configureEventBus(array $config, ContainerBuilder $container): void
     {
-        $container->register(SymfonyEventBus::class)
-            ->setArguments([new Reference($config['message_bus'])]);
+        if ($config['message_bus']) {
+            $container->register(SymfonyEventBus::class)
+                ->setArguments([new Reference($config['message_bus'])]);
 
-        $container->setAlias(EventBus::class, SymfonyEventBus::class);
+            $container->setAlias(EventBus::class, SymfonyEventBus::class);
+
+            $container->registerForAutoconfiguration(Listener::class)
+                ->addTag('messenger.message_handler', ['bus' => $config['message_bus']]);
+
+            return;
+        }
+
+        $container->register(DefaultEventBus::class);
+        $container->setAlias(EventBus::class, DefaultEventBus::class);
 
         $container->registerForAutoconfiguration(Listener::class)
-            ->addTag('messenger.message_handler', ['bus' => $config['message_bus']]);
+            ->addTag('event_sourcing.event_listener');
     }
 
     /**
-     * @param array{message_bus: string} $config
+     * @param array{message_bus: ?string} $config
      */
     private function configureProjection(array $config, ContainerBuilder $container): void
     {
-        $container->register(ProjectionListener::class)
-            ->setArguments([new Reference(ProjectionRepository::class)])
-            ->addTag('messenger.message_handler', ['bus' => $config['message_bus']]);
+        $projectionListener = $container->register(ProjectionListener::class)
+            ->setArguments([new Reference(ProjectionRepository::class)]);
+
+        if ($config['message_bus']) {
+            $projectionListener->addTag('messenger.message_handler', ['bus' => $config['message_bus']]);
+        } else {
+            $projectionListener->addTag('event_sourcing.event_listener');
+        }
 
         $container->registerForAutoconfiguration(Projection::class)
             ->addTag('event_sourcing.projection');
@@ -247,16 +263,21 @@ private function configureCommands(array $config, ContainerBuilder $container):
     }
 
     /**
-     * @param array{message_bus: string, watch_server: array{host: string}} $config
+     * @param array{message_bus: ?string, watch_server: array{host: string}} $config
      */
     private function configureWatchServer(array $config, ContainerBuilder $container): void
     {
         $container->register(WatchServerClient::class)
             ->setArguments([$config['watch_server']['host']]);
 
-        $container->register(WatchListener::class)
-            ->setArguments([new Reference(WatchServerClient::class)])
-            ->addTag('messenger.message_handler', ['bus' => $config['message_bus']]);
+        $listener = $container->register(WatchListener::class)
+            ->setArguments([new Reference(WatchServerClient::class)]);
+
+        if ($config['message_bus']) {
+            $listener->addTag('messenger.message_handler', ['bus' => $config['message_bus']]);
+        } else {
+            $listener->addTag('event_sourcing.event_listener');
+        }
 
         $container->register(WatchServer::class)
             ->setArguments([$config['watch_server']['host']]);
diff --git a/src/PatchlevelEventSourcingBundle.php b/src/PatchlevelEventSourcingBundle.php
index a7b8a337..e4855434 100644
--- a/src/PatchlevelEventSourcingBundle.php
+++ b/src/PatchlevelEventSourcingBundle.php
@@ -4,8 +4,16 @@
 
 namespace Patchlevel\EventSourcingBundle;
 
+use Patchlevel\EventSourcingBundle\DependencyInjection\Compiler\EventListenerPass;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\HttpKernel\Bundle\Bundle;
 
 class PatchlevelEventSourcingBundle extends Bundle
 {
+    public function build(ContainerBuilder $container): void
+    {
+        parent::build($container);
+
+        $container->addCompilerPass(new EventListenerPass());
+    }
 }