diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index 64403a5..e177c4c 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -8,7 +8,7 @@
 
 class Configuration implements ConfigurationInterface
 {
-    public function getConfigTreeBuilder()
+    public function getConfigTreeBuilder(): TreeBuilder
     {
         if (method_exists(TreeBuilder::class, 'getRootNode')) {
             $treeBuilder = new TreeBuilder('karser_recaptcha3');
diff --git a/DependencyInjection/KarserRecaptcha3Extension.php b/DependencyInjection/KarserRecaptcha3Extension.php
index f3eb619..c0002cf 100644
--- a/DependencyInjection/KarserRecaptcha3Extension.php
+++ b/DependencyInjection/KarserRecaptcha3Extension.php
@@ -10,7 +10,7 @@
 
 class KarserRecaptcha3Extension extends ConfigurableExtension implements PrependExtensionInterface
 {
-    public function loadInternal(array $configs, ContainerBuilder $container)
+    public function loadInternal(array $configs, ContainerBuilder $container): void
     {
         $loader = new Loader\PhpFileLoader($container, new FileLocator(__DIR__.'/../Resources/config'));
         $loader->load('services.php');
@@ -19,7 +19,7 @@ public function loadInternal(array $configs, ContainerBuilder $container)
         }
     }
 
-    public function prepend(ContainerBuilder $container)
+    public function prepend(ContainerBuilder $container): void
     {
         if ($container->hasExtension('twig')) {
             // inject template