diff --git a/src/Saml/ResponseContext.php b/src/Saml/ResponseContext.php
index ab29d0b..cbbcd5c 100644
--- a/src/Saml/ResponseContext.php
+++ b/src/Saml/ResponseContext.php
@@ -28,9 +28,9 @@
 final class ResponseContext implements ResponseContextInterface
 {
     public function __construct(
-        private IdentityProvider $hostedIdentityProvider,
-        private ServiceProviderRepository $serviceProviderRepository,
-        private StateHandlerInterface $stateHandler
+        private readonly IdentityProvider $hostedIdentityProvider,
+        private readonly ServiceProviderRepository $serviceProviderRepository,
+        private readonly StateHandlerInterface $stateHandler
     ) {
     }
 
diff --git a/src/Service/DateTime/StaticDateTimeService.php b/src/Service/DateTime/StaticDateTimeService.php
index 597b8ec..5b8e49c 100644
--- a/src/Service/DateTime/StaticDateTimeService.php
+++ b/src/Service/DateTime/StaticDateTimeService.php
@@ -25,11 +25,12 @@
 final class StaticDateTimeService extends AbstractDateTimeService
 {
 
-    public function __construct(private readonly DateTimeImmutable $dateTime)
-    {
+    public function __construct(
+        private readonly DateTimeImmutable $dateTime
+    ) {
     }
 
-    public function getCurrent(): \DateTimeImmutable
+    public function getCurrent(): DateTimeImmutable
     {
         return $this->dateTime;
     }
diff --git a/src/Service/ResponseService.php b/src/Service/ResponseService.php
index faa5ff3..9104cd8 100644
--- a/src/Service/ResponseService.php
+++ b/src/Service/ResponseService.php
@@ -35,10 +35,10 @@
 final class ResponseService implements ResponseServiceInterface
 {
     public function __construct(
-        private IdentityProvider $hostedIdentityProvider,
-        private ResponseContextInterface $responseContext,
-        private AssertionSigningServiceInterface $assertionSigningService,
-        private DateTimeService $dateTimeService
+        private readonly IdentityProvider $hostedIdentityProvider,
+        private readonly ResponseContextInterface $responseContext,
+        private readonly AssertionSigningServiceInterface $assertionSigningService,
+        private readonly DateTimeService $dateTimeService
     ) {
     }
 
diff --git a/src/Service/StateBasedAuthenticationService.php b/src/Service/StateBasedAuthenticationService.php
index 1a4e90c..d81c05b 100644
--- a/src/Service/StateBasedAuthenticationService.php
+++ b/src/Service/StateBasedAuthenticationService.php
@@ -35,9 +35,9 @@
 final class StateBasedAuthenticationService implements AuthenticationService
 {
     public function __construct(
-        private StateHandlerInterface $stateHandler,
-        private RouterInterface $router,
-        private LoggerInterface $logger
+        private readonly StateHandlerInterface $stateHandler,
+        private readonly RouterInterface $router,
+        private readonly LoggerInterface $logger
     ) {
     }
 
diff --git a/src/Service/StateBasedRegistrationService.php b/src/Service/StateBasedRegistrationService.php
index d7eeeaf..cfa37fc 100644
--- a/src/Service/StateBasedRegistrationService.php
+++ b/src/Service/StateBasedRegistrationService.php
@@ -34,9 +34,9 @@
 final class StateBasedRegistrationService implements RegistrationService
 {
     public function __construct(
-        private StateHandlerInterface $stateHandler,
-        private RouterInterface $router,
-        private LoggerInterface $logger
+        private readonly StateHandlerInterface $stateHandler,
+        private readonly RouterInterface $router,
+        private readonly LoggerInterface $logger
     ) {
     }
 
diff --git a/src/Service/StateHandler.php b/src/Service/StateHandler.php
index 1c3b35d..5f3ca96 100644
--- a/src/Service/StateHandler.php
+++ b/src/Service/StateHandler.php
@@ -25,8 +25,6 @@
 use Surfnet\SamlBundle\SAML2\Extensions\GsspUserAttributesChunk;
 use Surfnet\SamlBundle\SAML2\ReceivedAuthnRequest;
 use TypeError;
-use function is_string;
-use function sprintf;
 
 /**
  * Knows and preserves the integrity of the GSSP application state.