diff --git a/src/LazySession.php b/src/LazySession.php
index da327ba..2068dcf 100644
--- a/src/LazySession.php
+++ b/src/LazySession.php
@@ -23,19 +23,15 @@ final class LazySession implements
     SessionInterface,
     InitializeSessionIdInterface
 {
-    private SessionPersistenceInterface $persistence;
-
     private ?SessionInterface $proxiedSession = null;
 
-    /**
-     * Request instance to use when calling $persistence->initializeSessionFromRequest()
-     */
-    private ServerRequestInterface $request;
-
-    public function __construct(SessionPersistenceInterface $persistence, ServerRequestInterface $request)
-    {
-        $this->persistence = $persistence;
-        $this->request     = $request;
+    public function __construct(
+        private readonly SessionPersistenceInterface $persistence,
+        /**
+         * Request instance to use when calling $persistence->initializeSessionFromRequest()
+         */
+        private readonly ServerRequestInterface $request
+    ) {
     }
 
     public function regenerate(): SessionInterface
diff --git a/src/Session.php b/src/Session.php
index 2244784..bfadb01 100644
--- a/src/Session.php
+++ b/src/Session.php
@@ -23,17 +23,6 @@ class Session implements
      */
     private array $data;
 
-    /**
-     * The session identifier, if any.
-     *
-     * This is present in the session to allow the session persistence
-     * implementation to be stateless. When present here, we can query for it
-     * when it is time to persist the session, instead of relying on state in
-     * the persistence instance (which may be shared between multiple
-     * requests).
-     */
-    private string $id;
-
     private bool $isRegenerated = false;
 
     /**
@@ -49,10 +38,20 @@ class Session implements
     private int $sessionLifetime = 0;
 
     /** @param array<string, mixed> $data */
-    public function __construct(array $data, string $id = '')
-    {
+    public function __construct(
+        array $data,
+        /**
+         * The session identifier, if any.
+         *
+         * This is present in the session to allow the session persistence
+         * implementation to be stateless. When present here, we can query for it
+         * when it is time to persist the session, instead of relying on state in
+         * the persistence instance (which may be shared between multiple
+         * requests).
+         */
+        private string $id = ''
+    ) {
         $this->data = $this->originalData = $data;
-        $this->id   = $id;
 
         /** @psalm-suppress MixedAssignment */
         $lifetime = $data[SessionCookiePersistenceInterface::SESSION_LIFETIME_KEY] ?? null;
diff --git a/src/SessionMiddleware.php b/src/SessionMiddleware.php
index 611d035..927cfed 100644
--- a/src/SessionMiddleware.php
+++ b/src/SessionMiddleware.php
@@ -14,11 +14,8 @@ class SessionMiddleware implements MiddlewareInterface
 {
     public const SESSION_ATTRIBUTE = 'session';
 
-    private SessionPersistenceInterface $persistence;
-
-    public function __construct(SessionPersistenceInterface $persistence)
+    public function __construct(private readonly SessionPersistenceInterface $persistence)
     {
-        $this->persistence = $persistence;
     }
 
     public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
diff --git a/test/RequestHandler.php b/test/RequestHandler.php
index 4cb477f..6941717 100644
--- a/test/RequestHandler.php
+++ b/test/RequestHandler.php
@@ -13,7 +13,7 @@
 final class RequestHandler implements RequestHandlerInterface
 {
     private ?ServerRequestInterface $received = null;
-    private ResponseInterface $defaultResponse;
+    private readonly ResponseInterface $defaultResponse;
 
     public function __construct(
         ResponseInterface|null $defaultResponse = null,