diff --git a/Classes/Package.php b/Classes/Package.php
index cd71a3c..5abc0ea 100644
--- a/Classes/Package.php
+++ b/Classes/Package.php
@@ -32,7 +32,7 @@ class Package extends NeosFlowPackagePackage
         $dispatcher->connect(
             ConfigurationManager::class,
             'configurationManagerReady',
-            function (ConfigurationManager $configurationManager) {
+            function (ConfigurationManager $configurationManager): void {
                 $configurationManager->registerConfigurationType('Validation');
             }
         );
diff --git a/Migrations/Code/Version20170603120900.php b/Migrations/Code/Version20170603120900.php
index 144ed6d..7ca1548 100644
--- a/Migrations/Code/Version20170603120900.php
+++ b/Migrations/Code/Version20170603120900.php
@@ -19,7 +19,7 @@ class Version20170603120900 extends AbstractMigration
     {
         $this->processConfiguration(
             'Validation',
-            function (array &$configuration) {
+            function (array &$configuration): void {
                 foreach ($configuration as $validatorName => &$validators) {
                     // guard that protects configuration, which has already the new format:
                     if (isset($validators['properties']) || isset($validators['self'])) {