diff --git a/src/DependencyInjection/Configuration.php b/src/DependencyInjection/Configuration.php
index e282d4d..146e906 100644
--- a/src/DependencyInjection/Configuration.php
+++ b/src/DependencyInjection/Configuration.php
@@ -18,7 +18,7 @@
  */
 class Configuration implements ConfigurationInterface
 {
-    public function getConfigTreeBuilder()
+    public function getConfigTreeBuilder(): TreeBuilder
     {
         $treeBuilder = new TreeBuilder('symfonycasts_verify_email');
         $rootNode = $treeBuilder->getRootNode();
diff --git a/src/DependencyInjection/SymfonyCastsVerifyEmailExtension.php b/src/DependencyInjection/SymfonyCastsVerifyEmailExtension.php
index 1d59452..b5419e5 100644
--- a/src/DependencyInjection/SymfonyCastsVerifyEmailExtension.php
+++ b/src/DependencyInjection/SymfonyCastsVerifyEmailExtension.php
@@ -33,7 +33,7 @@ public function load(array $configs, ContainerBuilder $container): void
         $helperDefinition->replaceArgument(4, $config['lifetime']);
     }
 
-    public function getAlias()
+    public function getAlias(): string
     {
         return 'symfonycasts_verify_email';
     }
diff --git a/src/SymfonyCastsVerifyEmailBundle.php b/src/SymfonyCastsVerifyEmailBundle.php
index d8d61f8..f97a972 100644
--- a/src/SymfonyCastsVerifyEmailBundle.php
+++ b/src/SymfonyCastsVerifyEmailBundle.php
@@ -9,6 +9,7 @@
 
 namespace SymfonyCasts\Bundle\VerifyEmail;
 
+use Symfony\Component\DependencyInjection\Extension\ExtensionInterface;
 use Symfony\Component\HttpKernel\Bundle\Bundle;
 use SymfonyCasts\Bundle\VerifyEmail\DependencyInjection\SymfonyCastsVerifyEmailExtension;
 
@@ -18,7 +19,7 @@
  */
 class SymfonyCastsVerifyEmailBundle extends Bundle
 {
-    public function getContainerExtension()
+    public function getContainerExtension(): ?ExtensionInterface
     {
         if (null === $this->extension) {
             $this->extension = new SymfonyCastsVerifyEmailExtension();
diff --git a/tests/VerifyEmailTestKernel.php b/tests/VerifyEmailTestKernel.php
index 3ce626a..ebfc4ab 100644
--- a/tests/VerifyEmailTestKernel.php
+++ b/tests/VerifyEmailTestKernel.php
@@ -99,12 +99,12 @@ public function loadRoutes(LoaderInterface $loader): RouteCollection
         return $routes;
     }
 
-    public function getCacheDir()
+    public function getCacheDir(): string
     {
         return sys_get_temp_dir().'/cache'.spl_object_hash($this);
     }
 
-    public function getLogDir()
+    public function getLogDir(): string
     {
         return sys_get_temp_dir().'/logs'.spl_object_hash($this);
     }