diff --git a/src/Chartjs/tests/Kernel/TwigAppKernel.php b/src/Chartjs/tests/Kernel/TwigAppKernel.php
index 5d629bd2c88..76de3dbd28c 100644
--- a/src/Chartjs/tests/Kernel/TwigAppKernel.php
+++ b/src/Chartjs/tests/Kernel/TwigAppKernel.php
@@ -31,7 +31,7 @@ public function registerBundles(): iterable
         return [new FrameworkBundle(), new TwigBundle(), new StimulusBundle(), new ChartjsBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', ['secret' => '$ecret', 'test' => true, 'http_method_override' => false]);
diff --git a/src/Cropperjs/tests/Kernel/EmptyAppKernel.php b/src/Cropperjs/tests/Kernel/EmptyAppKernel.php
index 71926a9823b..a4a7c89bac8 100644
--- a/src/Cropperjs/tests/Kernel/EmptyAppKernel.php
+++ b/src/Cropperjs/tests/Kernel/EmptyAppKernel.php
@@ -29,7 +29,7 @@ public function registerBundles(): iterable
         return [new CropperjsBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
     }
 }
diff --git a/src/Cropperjs/tests/Kernel/FrameworkAppKernel.php b/src/Cropperjs/tests/Kernel/FrameworkAppKernel.php
index 1944eace20c..63535d3a2fb 100644
--- a/src/Cropperjs/tests/Kernel/FrameworkAppKernel.php
+++ b/src/Cropperjs/tests/Kernel/FrameworkAppKernel.php
@@ -31,7 +31,7 @@ public function registerBundles(): iterable
         return [new FrameworkBundle(), new CropperjsBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $frameworkConfig = [
diff --git a/src/Cropperjs/tests/Kernel/TwigAppKernel.php b/src/Cropperjs/tests/Kernel/TwigAppKernel.php
index 95cad5206c9..9b3a9ce84c3 100644
--- a/src/Cropperjs/tests/Kernel/TwigAppKernel.php
+++ b/src/Cropperjs/tests/Kernel/TwigAppKernel.php
@@ -34,7 +34,7 @@ public function registerBundles(): iterable
         return [new FrameworkBundle(), new TwigBundle(), new CropperjsBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $frameworkConfig = [
diff --git a/src/Dropzone/src/DependencyInjection/DropzoneExtension.php b/src/Dropzone/src/DependencyInjection/DropzoneExtension.php
index a40bc5fff68..697d1249840 100644
--- a/src/Dropzone/src/DependencyInjection/DropzoneExtension.php
+++ b/src/Dropzone/src/DependencyInjection/DropzoneExtension.php
@@ -25,7 +25,7 @@
  */
 class DropzoneExtension extends Extension implements PrependExtensionInterface
 {
-    public function prepend(ContainerBuilder $container)
+    public function prepend(ContainerBuilder $container): void
     {
         // Register the Dropzone form theme if TwigBundle is available
         $bundles = $container->getParameter('kernel.bundles');
diff --git a/src/Dropzone/tests/Kernel/EmptyAppKernel.php b/src/Dropzone/tests/Kernel/EmptyAppKernel.php
index f5734e0a5ce..e1541b7724e 100644
--- a/src/Dropzone/tests/Kernel/EmptyAppKernel.php
+++ b/src/Dropzone/tests/Kernel/EmptyAppKernel.php
@@ -29,7 +29,7 @@ public function registerBundles(): iterable
         return [new DropzoneBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
     }
 }
diff --git a/src/Dropzone/tests/Kernel/FrameworkAppKernel.php b/src/Dropzone/tests/Kernel/FrameworkAppKernel.php
index 4ab07836bd5..0198c6743db 100644
--- a/src/Dropzone/tests/Kernel/FrameworkAppKernel.php
+++ b/src/Dropzone/tests/Kernel/FrameworkAppKernel.php
@@ -31,7 +31,7 @@ public function registerBundles(): iterable
         return [new FrameworkBundle(), new DropzoneBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', ['secret' => '$ecret', 'test' => true]);
diff --git a/src/Dropzone/tests/Kernel/TwigAppKernel.php b/src/Dropzone/tests/Kernel/TwigAppKernel.php
index 8970425ab72..0da830a90f8 100644
--- a/src/Dropzone/tests/Kernel/TwigAppKernel.php
+++ b/src/Dropzone/tests/Kernel/TwigAppKernel.php
@@ -34,7 +34,7 @@ public function registerBundles(): iterable
         return [new FrameworkBundle(), new TwigBundle(), new DropzoneBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', ['secret' => '$ecret', 'test' => true, 'http_method_override' => false]);
diff --git a/src/LazyImage/tests/BlurHash/BlurHashTest.php b/src/LazyImage/tests/BlurHash/BlurHashTest.php
index 60baaf42982..1304d1bbdca 100644
--- a/src/LazyImage/tests/BlurHash/BlurHashTest.php
+++ b/src/LazyImage/tests/BlurHash/BlurHashTest.php
@@ -47,7 +47,7 @@ public function testEncode()
     public function testWithCustomGetImageContent(): void
     {
         $kernel = new class('test', true) extends TwigAppKernel {
-            public function registerContainerConfiguration(LoaderInterface $loader)
+            public function registerContainerConfiguration(LoaderInterface $loader): void
             {
                 parent::registerContainerConfiguration($loader);
 
@@ -99,7 +99,7 @@ public function testEnsureCacheIsNotUsedWhenNotConfigured()
     public function testEnsureCacheIsUsedWhenConfigured()
     {
         $kernel = new class('test', true) extends TwigAppKernel {
-            public function registerContainerConfiguration(LoaderInterface $loader)
+            public function registerContainerConfiguration(LoaderInterface $loader): void
             {
                 parent::registerContainerConfiguration($loader);
 
@@ -154,7 +154,7 @@ public function testCreateDataUriThumbnail()
     public function testCreateDataUriThumbnailWithCache()
     {
         $kernel = new class('test', true) extends TwigAppKernel {
-            public function registerContainerConfiguration(LoaderInterface $loader)
+            public function registerContainerConfiguration(LoaderInterface $loader): void
             {
                 parent::registerContainerConfiguration($loader);
 
diff --git a/src/LazyImage/tests/Kernel/EmptyAppKernel.php b/src/LazyImage/tests/Kernel/EmptyAppKernel.php
index 4d215d31c28..03394163784 100644
--- a/src/LazyImage/tests/Kernel/EmptyAppKernel.php
+++ b/src/LazyImage/tests/Kernel/EmptyAppKernel.php
@@ -29,7 +29,7 @@ public function registerBundles(): iterable
         return [new LazyImageBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
     }
 }
diff --git a/src/LazyImage/tests/Kernel/FrameworkAppKernel.php b/src/LazyImage/tests/Kernel/FrameworkAppKernel.php
index 2dd2e4b7d29..dac1de8118f 100644
--- a/src/LazyImage/tests/Kernel/FrameworkAppKernel.php
+++ b/src/LazyImage/tests/Kernel/FrameworkAppKernel.php
@@ -31,7 +31,7 @@ public function registerBundles(): iterable
         return [new FrameworkBundle(), new LazyImageBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', ['secret' => '$ecret', 'test' => true]);
diff --git a/src/LazyImage/tests/Kernel/TwigAppKernel.php b/src/LazyImage/tests/Kernel/TwigAppKernel.php
index 185798d31dd..51869833765 100644
--- a/src/LazyImage/tests/Kernel/TwigAppKernel.php
+++ b/src/LazyImage/tests/Kernel/TwigAppKernel.php
@@ -32,7 +32,7 @@ public function registerBundles(): iterable
         return [new FrameworkBundle(), new TwigBundle(), new LazyImageBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', ['secret' => '$ecret', 'test' => true, 'http_method_override' => false]);
diff --git a/src/Notify/tests/Kernel/TwigAppKernel.php b/src/Notify/tests/Kernel/TwigAppKernel.php
index de278e8fcdc..59910fd30eb 100644
--- a/src/Notify/tests/Kernel/TwigAppKernel.php
+++ b/src/Notify/tests/Kernel/TwigAppKernel.php
@@ -36,7 +36,7 @@ public function registerBundles(): iterable
         yield new NotifyBundle();
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', ['secret' => '$ecret', 'test' => true, 'http_method_override' => false]);
diff --git a/src/React/tests/Kernel/TwigAppKernel.php b/src/React/tests/Kernel/TwigAppKernel.php
index cb1027ddde3..762c1bcbe87 100644
--- a/src/React/tests/Kernel/TwigAppKernel.php
+++ b/src/React/tests/Kernel/TwigAppKernel.php
@@ -31,7 +31,7 @@ public function registerBundles(): iterable
         return [new FrameworkBundle(), new StimulusBundle(), new TwigBundle(), new ReactBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', ['secret' => '$ecret', 'test' => true, 'http_method_override' => false]);
diff --git a/src/StimulusBundle/src/DependencyInjection/StimulusExtension.php b/src/StimulusBundle/src/DependencyInjection/StimulusExtension.php
index aa0a1060bb2..97a7ec2f993 100644
--- a/src/StimulusBundle/src/DependencyInjection/StimulusExtension.php
+++ b/src/StimulusBundle/src/DependencyInjection/StimulusExtension.php
@@ -43,7 +43,7 @@ public function load(array $configs, ContainerBuilder $container): void
         }
     }
 
-    public function prepend(ContainerBuilder $container)
+    public function prepend(ContainerBuilder $container): void
     {
         if (!$this->isAssetMapperAvailable($container)) {
             return;
diff --git a/src/Svelte/tests/Kernel/TwigAppKernel.php b/src/Svelte/tests/Kernel/TwigAppKernel.php
index e61a638665b..29c82c6ff13 100644
--- a/src/Svelte/tests/Kernel/TwigAppKernel.php
+++ b/src/Svelte/tests/Kernel/TwigAppKernel.php
@@ -32,7 +32,7 @@ public function registerBundles(): iterable
         return [new StimulusBundle(), new FrameworkBundle(), new TwigBundle(), new SvelteBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', ['secret' => '$ecret', 'test' => true, 'http_method_override' => false]);
diff --git a/src/Translator/src/DependencyInjection/UxTranslatorExtension.php b/src/Translator/src/DependencyInjection/UxTranslatorExtension.php
index 9ba3a02926c..3ebfbe518e9 100644
--- a/src/Translator/src/DependencyInjection/UxTranslatorExtension.php
+++ b/src/Translator/src/DependencyInjection/UxTranslatorExtension.php
@@ -27,7 +27,7 @@
  */
 class UxTranslatorExtension extends Extension implements PrependExtensionInterface
 {
-    public function load(array $configs, ContainerBuilder $container)
+    public function load(array $configs, ContainerBuilder $container): void
     {
         $configuration = new Configuration();
         $config = $this->processConfiguration($configuration, $configs);
@@ -46,7 +46,7 @@ public function load(array $configs, ContainerBuilder $container)
         }
     }
 
-    public function prepend(ContainerBuilder $container)
+    public function prepend(ContainerBuilder $container): void
     {
         if (!$this->isAssetMapperAvailable($container)) {
             return;
diff --git a/src/Translator/tests/Kernel/EmptyAppKernel.php b/src/Translator/tests/Kernel/EmptyAppKernel.php
index 648443bc735..b92997f6fef 100644
--- a/src/Translator/tests/Kernel/EmptyAppKernel.php
+++ b/src/Translator/tests/Kernel/EmptyAppKernel.php
@@ -29,7 +29,7 @@ public function registerBundles(): iterable
         return [new UxTranslatorBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
     }
 }
diff --git a/src/Translator/tests/Kernel/FrameworkAppKernel.php b/src/Translator/tests/Kernel/FrameworkAppKernel.php
index 98c0ca6a703..3e61e1ef9d8 100644
--- a/src/Translator/tests/Kernel/FrameworkAppKernel.php
+++ b/src/Translator/tests/Kernel/FrameworkAppKernel.php
@@ -31,7 +31,7 @@ public function registerBundles(): iterable
         return [new FrameworkBundle(), new UxTranslatorBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', [
diff --git a/src/Vue/tests/Kernel/TwigAppKernel.php b/src/Vue/tests/Kernel/TwigAppKernel.php
index 5221f7e362f..54a5be3be5c 100644
--- a/src/Vue/tests/Kernel/TwigAppKernel.php
+++ b/src/Vue/tests/Kernel/TwigAppKernel.php
@@ -32,7 +32,7 @@ public function registerBundles(): iterable
         return [new StimulusBundle(), new FrameworkBundle(), new TwigBundle(), new VueBundle()];
     }
 
-    public function registerContainerConfiguration(LoaderInterface $loader)
+    public function registerContainerConfiguration(LoaderInterface $loader): void
     {
         $loader->load(function (ContainerBuilder $container) {
             $container->loadFromExtension('framework', ['secret' => '$ecret', 'test' => true, 'http_method_override' => false]);