diff --git a/Resources/Core/Functional/Extensions/private_container/Classes/DependencyInjection/PrivateContainerRealRefPass.php b/Resources/Core/Functional/Extensions/private_container/Classes/DependencyInjection/PrivateContainerRealRefPass.php
index 75da844a..d5a06760 100644
--- a/Resources/Core/Functional/Extensions/private_container/Classes/DependencyInjection/PrivateContainerRealRefPass.php
+++ b/Resources/Core/Functional/Extensions/private_container/Classes/DependencyInjection/PrivateContainerRealRefPass.php
@@ -27,7 +27,7 @@
  */
 class PrivateContainerRealRefPass implements CompilerPassInterface
 {
-    public function process(ContainerBuilder $container)
+    public function process(ContainerBuilder $container): void
     {
         if (!$container->hasDefinition('typo3.testing-framework.private-container')) {
             return;
diff --git a/Resources/Core/Functional/Extensions/private_container/Classes/DependencyInjection/PrivateContainerWeakRefPass.php b/Resources/Core/Functional/Extensions/private_container/Classes/DependencyInjection/PrivateContainerWeakRefPass.php
index 8ab7a312..3db9ddd2 100644
--- a/Resources/Core/Functional/Extensions/private_container/Classes/DependencyInjection/PrivateContainerWeakRefPass.php
+++ b/Resources/Core/Functional/Extensions/private_container/Classes/DependencyInjection/PrivateContainerWeakRefPass.php
@@ -29,7 +29,7 @@
  */
 class PrivateContainerWeakRefPass implements CompilerPassInterface
 {
-    public function process(ContainerBuilder $container)
+    public function process(ContainerBuilder $container): void
     {
         $privateServices = [];
         $definitions = $container->getDefinitions();