diff --git a/src/KibokoSyliusPayzenBundle.php b/src/KibokoSyliusPayzenBundle.php
index ea79970..2230fcb 100755
--- a/src/KibokoSyliusPayzenBundle.php
+++ b/src/KibokoSyliusPayzenBundle.php
@@ -3,11 +3,12 @@
 namespace Kiboko\SyliusPayzenBundle;
 
 use Kiboko\SyliusPayzenBundle\DependencyInjection\KibokoSyliusPayzenExtension;
+use Symfony\Component\DependencyInjection\Extension\ExtensionInterface;
 use Symfony\Component\HttpKernel\Bundle\Bundle;
 
 final class KibokoSyliusPayzenBundle extends Bundle
 {
-    public function getContainerExtension()
+    public function getContainerExtension(): ?ExtensionInterface
     {
         if (null === $this->extension) {
             $this->extension = new KibokoSyliusPayzenExtension();