diff --git a/src/MessageTrait.php b/src/MessageTrait.php
index e95d072a..87cd267a 100644
--- a/src/MessageTrait.php
+++ b/src/MessageTrait.php
@@ -30,24 +30,20 @@ trait MessageTrait
     /**
      * List of all registered headers, as key => array of values.
      *
-     * @var array
      * @psalm-var array<non-empty-string, list<string>>
      */
-    protected $headers = [];
+    protected array $headers = [];
 
     /**
      * Map of normalized header name to original name used to register header.
      *
-     * @var array
      * @psalm-var array<non-empty-string, non-empty-string>
      */
-    protected $headerNames = [];
+    protected array $headerNames = [];
 
-    /** @var string */
-    private $protocol = '1.1';
+    private string $protocol = '1.1';
 
-    /** @var StreamInterface */
-    private $stream;
+    private StreamInterface $stream;
 
     /**
      * Retrieves the HTTP protocol version as a string.
diff --git a/src/Request/ArraySerializer.php b/src/Request/ArraySerializer.php
index e3c10485..58fe17e4 100644
--- a/src/Request/ArraySerializer.php
+++ b/src/Request/ArraySerializer.php
@@ -70,10 +70,9 @@ public static function fromArray(array $serializedRequest): Request
     }
 
     /**
-     * @return mixed
      * @throws Exception\DeserializationException
      */
-    private static function getValueFromKey(array $data, string $key, ?string $message = null)
+    private static function getValueFromKey(array $data, string $key, ?string $message = null): mixed
     {
         if (isset($data[$key])) {
             return $data[$key];
diff --git a/src/RequestTrait.php b/src/RequestTrait.php
index e8519a36..3717ee9b 100644
--- a/src/RequestTrait.php
+++ b/src/RequestTrait.php
@@ -28,18 +28,14 @@ trait RequestTrait
 {
     use MessageTrait;
 
-    /** @var string */
-    private $method = 'GET';
+    private string $method = 'GET';
 
     /**
      * The request-target, if it has been provided or calculated.
-     *
-     * @var null|string
      */
-    private $requestTarget;
+    private ?string $requestTarget = null;
 
-    /** @var UriInterface */
-    private $uri;
+    private UriInterface $uri;
 
     /**
      * Initialize request state.
diff --git a/src/Response/ArraySerializer.php b/src/Response/ArraySerializer.php
index 0828e798..ddbf17bc 100644
--- a/src/Response/ArraySerializer.php
+++ b/src/Response/ArraySerializer.php
@@ -68,10 +68,9 @@ public static function fromArray(array $serializedResponse): Response
     }
 
     /**
-     * @return mixed
      * @throws Exception\DeserializationException
      */
-    private static function getValueFromKey(array $data, string $key, ?string $message = null)
+    private static function getValueFromKey(array $data, string $key, ?string $message = null): mixed
     {
         if (isset($data[$key])) {
             return $data[$key];
diff --git a/src/Response/JsonResponse.php b/src/Response/JsonResponse.php
index f570a0a0..96fc6b21 100644
--- a/src/Response/JsonResponse.php
+++ b/src/Response/JsonResponse.php
@@ -43,8 +43,7 @@ class JsonResponse extends Response
         | JSON_HEX_QUOT
         | JSON_UNESCAPED_SLASHES;
 
-    /** @var mixed */
-    private $payload;
+    private mixed $payload;
 
     /**
      * Create a JSON response with the given data.
@@ -65,7 +64,7 @@ class JsonResponse extends Response
      * @throws Exception\InvalidArgumentException If unable to encode the $data to JSON.
      */
     public function __construct(
-        $data,
+        mixed $data,
         int $status = 200,
         array $headers = [],
         private int $encodingOptions = self::DEFAULT_JSON_FLAGS
@@ -80,10 +79,7 @@ public function __construct(
         parent::__construct($body, $status, $headers);
     }
 
-    /**
-     * @return mixed
-     */
-    public function getPayload()
+    public function getPayload(): mixed
     {
         return $this->payload;
     }
diff --git a/src/Uri.php b/src/Uri.php
index 0c35fdc6..51afbfff 100644
--- a/src/Uri.php
+++ b/src/Uri.php
@@ -53,7 +53,7 @@ class Uri implements UriInterface, Stringable
     public const CHAR_UNRESERVED = 'a-zA-Z0-9_\-\.~\pL';
 
     /** @var int[] Array indexed by valid scheme names to their corresponding ports. */
-    protected $allowedSchemes = [
+    protected array $allowedSchemes = [
         'http'  => 80,
         'https' => 443,
     ];