diff --git a/src/FlashMessageMiddleware.php b/src/FlashMessageMiddleware.php
index 946aff3..724974c 100644
--- a/src/FlashMessageMiddleware.php
+++ b/src/FlashMessageMiddleware.php
@@ -17,14 +17,12 @@ class FlashMessageMiddleware implements MiddlewareInterface
 {
     public const FLASH_ATTRIBUTE = 'flash';
 
-    /** @var string */
-    private $attributeKey;
+    private string $attributeKey;
 
     /** @psalm-var callable(SessionInterface, string): FlashMessagesInterface */
     private $flashMessageFactory;
 
-    /** @var string */
-    private $sessionKey;
+    private string $sessionKey;
 
     public function __construct(
         string $flashMessagesClass = FlashMessages::class,
diff --git a/src/FlashMessages.php b/src/FlashMessages.php
index dabd263..373c182 100644
--- a/src/FlashMessages.php
+++ b/src/FlashMessages.php
@@ -30,13 +30,11 @@
 class FlashMessages implements FlashMessagesInterface
 {
     /** @var array<string,mixed> */
-    private $currentMessages = [];
+    private array $currentMessages = [];
 
-    /** @var SessionInterface */
-    private $session;
+    private SessionInterface $session;
 
-    /** @var string */
-    private $sessionKey;
+    private string $sessionKey;
 
     private function __construct(SessionInterface $session, string $sessionKey)
     {
diff --git a/test/ConfigProviderTest.php b/test/ConfigProviderTest.php
index 159bd1b..2d3bc30 100644
--- a/test/ConfigProviderTest.php
+++ b/test/ConfigProviderTest.php
@@ -9,8 +9,7 @@
 
 class ConfigProviderTest extends TestCase
 {
-    /** @var ConfigProvider */
-    private $provider;
+    private ConfigProvider $provider;
 
     public function setUp(): void
     {
diff --git a/test/FlashMessageMiddlewareTest.php b/test/FlashMessageMiddlewareTest.php
index 9481692..94e84ce 100644
--- a/test/FlashMessageMiddlewareTest.php
+++ b/test/FlashMessageMiddlewareTest.php
@@ -78,7 +78,7 @@ public function testProcessUsesConfiguredClassAndSessionKeyAndAttributeKeyToCrea
             ->method('withAttribute')
             ->with(
                 'non-standard-flash-attr',
-                $this->callback(function (TestAsset\FlashMessages $flash) use ($session) {
+                $this->callback(function (TestAsset\FlashMessages $flash) use ($session): bool {
                     $this->assertSame($session, $flash->session);
                     $this->assertSame('non-standard-flash-next', $flash->sessionKey);
                     return true;