diff --git a/src/PuliServiceProvider.php b/src/PuliServiceProvider.php
index cfcc5ea..03422d7 100644
--- a/src/PuliServiceProvider.php
+++ b/src/PuliServiceProvider.php
@@ -15,6 +15,7 @@
 use Puli\TwigExtension\PuliTemplateLoader;
 use Silex\Application;
 use Silex\ServiceProviderInterface;
+use Twig_Loader_Chain;
 
 class PuliServiceProvider implements ServiceProviderInterface
 {
@@ -54,12 +55,24 @@ public function register(Application $app)
      */
     public function boot(Application $app)
     {
-        if (isset($app['twig']) && $app['puli.enable_twig']) {
-            $app['twig.loader'] = $app->share(function (Application $app) {
-                return new PuliTemplateLoader($app['puli.repository']);
-            });
-
-            $app['twig']->addExtension(new PuliExtension($app['puli.repository'], $app['puli.asset_url_generator']));
+        if (!isset($app['twig']) || !$app['puli.enable_twig']) {
+            return;
         }
+
+        $app->extend('twig.loader', function ($twigLoader, $app) {
+            if (!$twigLoader instanceof Twig_Loader_Chain) {
+                $twigLoader = new Twig_Loader_Chain(array($twigLoader));
+            }
+
+            $twigLoader->addLoader(new PuliTemplateLoader($app['puli.repository']));
+
+            return $twigLoader;
+        });
+
+        $app->extend('twig', function ($twig, $app) {
+            $twig->addExtension(new PuliExtension($app['puli.repository'], $app['puli.asset_url_generator']));
+
+            return $twig;
+        });
     }
 }
diff --git a/tests/PuliServiceProviderTest.php b/tests/PuliServiceProviderTest.php
index d34c8f4..ba7c318 100644
--- a/tests/PuliServiceProviderTest.php
+++ b/tests/PuliServiceProviderTest.php
@@ -11,10 +11,13 @@
 
 namespace Puli\SilexProvider\Tests;
 
+use PHPUnit_Framework_Assert;
 use PHPUnit_Framework_TestCase;
 use Puli\SilexProvider\PuliServiceProvider;
+use Puli\TwigExtension\PuliTemplateLoader;
 use Silex\Application;
 use Silex\Provider\TwigServiceProvider;
+use Twig_Loader_Array;
 
 class PuliServiceProviderTest extends PHPUnit_Framework_TestCase
 {
@@ -38,7 +41,37 @@ public function testConfiguredApplicationWithTwigExtension()
         $app->boot();
 
         $this->assertTrue($app['twig']->hasExtension('puli'));
-        $this->assertInstanceOf('Puli\TwigExtension\PuliTemplateLoader', $app['twig.loader']);
+
+        $loaders = PHPUnit_Framework_Assert::readAttribute($app['twig.loader'], 'loaders');
+        $puliLoaders = array_filter($loaders, function ($loader) {
+            return !$loader instanceof PuliTemplateLoader;
+        });
+
+        $this->assertNotEmpty($puliLoaders);
+    }
+
+    public function testConfiguredApplicationWithTwigExtensionAndLoader()
+    {
+        $app = new Application();
+
+        $app->register(new TwigServiceProvider());
+        $app['twig.loader'] = function () {
+            return new Twig_Loader_Array(array());
+        };
+
+        $app->register(new PuliServiceProvider());
+        $app->boot();
+
+        $this->assertTrue($app['twig']->hasExtension('puli'));
+
+        $loaders = PHPUnit_Framework_Assert::readAttribute($app['twig.loader'], 'loaders');
+
+        $this->assertNotEmpty(array_filter($loaders, function ($loader) {
+            return !$loader instanceof PuliTemplateLoader;
+        }));
+        $this->assertNotEmpty(array_filter($loaders, function ($loader) {
+            return !$loader instanceof Twig_Loader_Array;
+        }));
     }
 
     public function testConfiguredApplicationWithTwigExtensionDisabled()
@@ -51,6 +84,12 @@ public function testConfiguredApplicationWithTwigExtensionDisabled()
         $app->boot();
 
         $this->assertFalse($app['twig']->hasExtension('puli'));
-        $this->assertNotInstanceOf('Puli\TwigExtension\PuliTemplateLoader', $app['twig.loader']);
+
+        $loaders = PHPUnit_Framework_Assert::readAttribute($app['twig.loader'], 'loaders');
+        $puliLoaders = array_filter($loaders, function ($loader) {
+            return $loader instanceof PuliTemplateLoader;
+        });
+
+        $this->assertEmpty($puliLoaders);
     }
 }