diff --git a/src/Response.php b/src/Response.php
index a13030c..b4c2672 100644
--- a/src/Response.php
+++ b/src/Response.php
@@ -209,13 +209,13 @@ public function hasHeader($name)
      *
      * @param string $name Case-insensitive header field name to add.
      * @param string|string[] $value Header value(s).
-     * @return Response
+     * @return static
      * @throws InvalidArgumentException for invalid header names or values.
      */
     public function withAddedHeader($name, $value)
     {
         $response = $this->response->withAddedHeader($name, $value);
-        return new Response($response, $this->streamFactory);
+        return new static($response, $this->streamFactory);
     }
 
     /**
@@ -228,13 +228,13 @@ public function withAddedHeader($name, $value)
      * new body stream.
      *
      * @param StreamInterface $body Body.
-     * @return Response
+     * @return static
      * @throws InvalidArgumentException When the body is not valid.
      */
     public function withBody(StreamInterface $body)
     {
         $response = $this->response->withBody($body);
-        return new Response($response, $this->streamFactory);
+        return new static($response, $this->streamFactory);
     }
 
     /**
@@ -249,13 +249,13 @@ public function withBody(StreamInterface $body)
      *
      * @param string $name Case-insensitive header field name.
      * @param string|string[] $value Header value(s).
-     * @return Response
+     * @return static
      * @throws InvalidArgumentException for invalid header names or values.
      */
     public function withHeader($name, $value)
     {
         $response = $this->response->withHeader($name, $value);
-        return new Response($response, $this->streamFactory);
+        return new static($response, $this->streamFactory);
     }
 
     /**
@@ -268,12 +268,12 @@ public function withHeader($name, $value)
      * the named header.
      *
      * @param string $name Case-insensitive header field name to remove.
-     * @return Response
+     * @return static
      */
     public function withoutHeader($name)
     {
         $response = $this->response->withoutHeader($name);
-        return new Response($response, $this->streamFactory);
+        return new static($response, $this->streamFactory);
     }
 
     /**
@@ -287,12 +287,12 @@ public function withoutHeader($name)
      * new protocol version.
      *
      * @param string $version HTTP protocol version
-     * @return Response
+     * @return static
      */
     public function withProtocolVersion($version)
     {
         $response = $this->response->withProtocolVersion($version);
-        return new Response($response, $this->streamFactory);
+        return new static($response, $this->streamFactory);
     }
 
     /**
@@ -312,13 +312,13 @@ public function withProtocolVersion($version)
      * @param string $reasonPhrase The reason phrase to use with the
      *     provided status code; if none is provided, implementations MAY
      *     use the defaults as suggested in the HTTP specification.
-     * @return Response
+     * @return static
      * @throws InvalidArgumentException For invalid status code arguments.
      */
     public function withStatus($code, $reasonPhrase = '')
     {
         $response = $this->response->withStatus($code, $reasonPhrase);
-        return new Response($response, $this->streamFactory);
+        return new static($response, $this->streamFactory);
     }
 
     /**
@@ -333,7 +333,7 @@ public function withStatus($code, $reasonPhrase = '')
      * @param  int    $status The HTTP status code.
      * @param  int    $options Json encoding options
      * @param  int    $depth Json encoding max depth
-     * @return Response
+     * @return static
      */
     public function withJson($data, int $status = null, int $options = 0, int $depth = 512): ResponseInterface
     {
@@ -351,7 +351,7 @@ public function withJson($data, int $status = null, int $options = 0, int $depth
             $response = $response->withStatus($status);
         }
 
-        return new Response($response, $this->streamFactory);
+        return new static($response, $this->streamFactory);
     }
 
     /**
@@ -364,7 +364,7 @@ public function withJson($data, int $status = null, int $options = 0, int $depth
      *
      * @param string $url The redirect destination.
      * @param int|null $status The redirect HTTP status code.
-     * @return Response
+     * @return static
      */
     public function withRedirect(string $url, $status = null): ResponseInterface
     {
@@ -375,7 +375,7 @@ public function withRedirect(string $url, $status = null): ResponseInterface
         }
         $response = $response->withStatus($status);
 
-        return new Response($response, $this->streamFactory);
+        return new static($response, $this->streamFactory);
     }
 
     /**
@@ -386,9 +386,9 @@ public function withRedirect(string $url, $status = null): ResponseInterface
      * Proxies to the underlying stream and writes the provided data to it.
      *
      * @param string $data
-     * @return self
+     * @return static
      */
-    public function write($data)
+    public function write($data): ResponseInterface
     {
         $this->response->getBody()->write($data);
         return $this;
diff --git a/src/ServerRequest.php b/src/ServerRequest.php
index 3f0828f..2193111 100644
--- a/src/ServerRequest.php
+++ b/src/ServerRequest.php
@@ -423,13 +423,13 @@ public function hasHeader($name)
      *
      * @param string $name Case-insensitive header field name to add.
      * @param string|string[] $value Header value(s).
-     * @return ServerRequest
+     * @return static
      * @throws InvalidArgumentException for invalid header names or values.
      */
     public function withAddedHeader($name, $value)
     {
         $serverRequest = $this->serverRequest->withAddedHeader($name, $value);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -445,12 +445,12 @@ public function withAddedHeader($name, $value)
      * @see getAttributes()
      * @param string $name The attribute name.
      * @param mixed $value The value of the attribute.
-     * @return ServerRequest
+     * @return static
      */
     public function withAttribute($name, $value)
     {
         $serverRequest = $this->serverRequest->withAttribute($name, $value);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -466,7 +466,7 @@ public function withAttribute($name, $value)
      * updated attributes.
      *
      * @param  array $attributes New attributes
-     * @return ServerRequest
+     * @return static
      */
     public function withAttributes(array $attributes)
     {
@@ -476,7 +476,7 @@ public function withAttributes(array $attributes)
             $serverRequest = $serverRequest->withAttribute($attribute, $value);
         }
 
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -491,12 +491,12 @@ public function withAttributes(array $attributes)
      *
      * @see getAttributes()
      * @param string $name The attribute name.
-     * @return ServerRequest
+     * @return static
      */
     public function withoutAttribute($name)
     {
         $serverRequest = $this->serverRequest->withoutAttribute($name);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -509,13 +509,13 @@ public function withoutAttribute($name)
      * new body stream.
      *
      * @param StreamInterface $body Body.
-     * @return ServerRequest
+     * @return static
      * @throws InvalidArgumentException When the body is not valid.
      */
     public function withBody(StreamInterface $body)
     {
         $serverRequest = $this->serverRequest->withBody($body);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -533,12 +533,12 @@ public function withBody(StreamInterface $body)
      * updated cookie values.
      *
      * @param array $cookies Array of key/value pairs representing cookies.
-     * @return ServerRequest
+     * @return static
      */
     public function withCookieParams(array $cookies)
     {
         $serverRequest = $this->serverRequest->withCookieParams($cookies);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -553,13 +553,13 @@ public function withCookieParams(array $cookies)
      *
      * @param string $name Case-insensitive header field name.
      * @param string|string[] $value Header value(s).
-     * @return ServerRequest
+     * @return static
      * @throws InvalidArgumentException for invalid header names or values.
      */
     public function withHeader($name, $value)
     {
         $serverRequest = $this->serverRequest->withHeader($name, $value);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -572,12 +572,12 @@ public function withHeader($name, $value)
      * the named header.
      *
      * @param string $name Case-insensitive header field name to remove.
-     * @return ServerRequest
+     * @return static
      */
     public function withoutHeader($name)
     {
         $serverRequest = $this->serverRequest->withoutHeader($name);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -592,13 +592,13 @@ public function withoutHeader($name)
      * changed request method.
      *
      * @param string $method Case-sensitive method.
-     * @return ServerRequest
+     * @return static
      * @throws InvalidArgumentException for invalid HTTP methods.
      */
     public function withMethod($method)
     {
         $serverRequest = $this->serverRequest->withMethod($method);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -625,14 +625,14 @@ public function withMethod($method)
      *
      * @param null|array|object $data The deserialized body data. This will
      *     typically be in an array or object.
-     * @return ServerRequest
+     * @return static
      * @throws InvalidArgumentException if an unsupported argument type is
      *     provided.
      */
     public function withParsedBody($data)
     {
         $serverRequest = $this->serverRequest->withParsedBody($data);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -646,12 +646,12 @@ public function withParsedBody($data)
      * new protocol version.
      *
      * @param string $version HTTP protocol version
-     * @return ServerRequest
+     * @return static
      */
     public function withProtocolVersion($version)
     {
         $serverRequest = $this->serverRequest->withProtocolVersion($version);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -674,12 +674,12 @@ public function withProtocolVersion($version)
      *
      * @param array $query Array of query string arguments, typically from
      *     $_GET.
-     * @return ServerRequest
+     * @return static
      */
     public function withQueryParams(array $query)
     {
         $serverRequest = $this->serverRequest->withQueryParams($query);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -697,12 +697,12 @@ public function withQueryParams(array $query)
      * @link http://tools.ietf.org/html/rfc7230#section-5.3 (for the various
      *     request-target forms allowed in request messages)
      * @param mixed $requestTarget
-     * @return ServerRequest
+     * @return static
      */
     public function withRequestTarget($requestTarget)
     {
         $serverRequest = $this->serverRequest->withRequestTarget($requestTarget);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -713,13 +713,13 @@ public function withRequestTarget($requestTarget)
      * updated body parameters.
      *
      * @param array $uploadedFiles An array tree of UploadedFileInterface instances.
-     * @return ServerRequest
+     * @return static
      * @throws InvalidArgumentException if an invalid structure is provided.
      */
     public function withUploadedFiles(array $uploadedFiles)
     {
         $serverRequest = $this->serverRequest->withUploadedFiles($uploadedFiles);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -750,12 +750,12 @@ public function withUploadedFiles(array $uploadedFiles)
      * @link http://tools.ietf.org/html/rfc3986#section-4.3
      * @param UriInterface $uri New request URI to use.
      * @param bool $preserveHost Preserve the original state of the Host header.
-     * @return ServerRequest
+     * @return static
      */
     public function withUri(UriInterface $uri, $preserveHost = false)
     {
         $serverRequest = $this->serverRequest->withUri($uri, $preserveHost);
-        return new ServerRequest($serverRequest);
+        return new static($serverRequest);
     }
 
     /**
@@ -986,9 +986,9 @@ public function getServerParam($key, $default = null)
      *
      * @param string   $mediaType A HTTP media type (excluding content-type params).
      * @param callable $callable  A callable that returns parsed contents for media type.
-     * @return self
+     * @return static
      */
-    public function registerMediaTypeParser($mediaType, callable $callable)
+    public function registerMediaTypeParser($mediaType, callable $callable): ServerRequestInterface
     {
         if ($callable instanceof Closure) {
             $callable = $callable->bindTo($this);
diff --git a/src/Uri.php b/src/Uri.php
index 761967a..c32ccb5 100644
--- a/src/Uri.php
+++ b/src/Uri.php
@@ -226,12 +226,12 @@ public function getUserInfo()
      * An empty fragment value is equivalent to removing the fragment.
      *
      * @param string $fragment The fragment to use with the new instance.
-     * @return Uri A new instance with the specified fragment.
+     * @return static A new instance with the specified fragment.
      */
     public function withFragment($fragment)
     {
         $uri = $this->uri->withFragment($fragment);
-        return new Uri($uri);
+        return new static($uri);
     }
 
     /**
@@ -243,13 +243,13 @@ public function withFragment($fragment)
      * An empty host value is equivalent to removing the host.
      *
      * @param string $host The hostname to use with the new instance.
-     * @return Uri A new instance with the specified host.
+     * @return static A new instance with the specified host.
      * @throws InvalidArgumentException for invalid hostnames.
      */
     public function withHost($host)
     {
         $uri = $this->uri->withHost($host);
-        return new Uri($uri);
+        return new static($uri);
     }
 
     /**
@@ -271,13 +271,13 @@ public function withHost($host)
      * Implementations ensure the correct encoding as outlined in getPath().
      *
      * @param string $path The path to use with the new instance.
-     * @return Uri A new instance with the specified path.
+     * @return static A new instance with the specified path.
      * @throws InvalidArgumentException for invalid paths.
      */
     public function withPath($path)
     {
         $uri = $this->uri->withPath($path);
-        return new Uri($uri);
+        return new static($uri);
     }
 
     /**
@@ -294,13 +294,13 @@ public function withPath($path)
      *
      * @param null|int $port The port to use with the new instance; a null value
      *     removes the port information.
-     * @return Uri A new instance with the specified port.
+     * @return static A new instance with the specified port.
      * @throws InvalidArgumentException for invalid ports.
      */
     public function withPort($port)
     {
         $uri = $this->uri->withPort($port);
-        return new Uri($uri);
+        return new static($uri);
     }
 
     /**
@@ -315,13 +315,13 @@ public function withPort($port)
      * An empty query string value is equivalent to removing the query string.
      *
      * @param string $query The query string to use with the new instance.
-     * @return Uri A new instance with the specified query string.
+     * @return static A new instance with the specified query string.
      * @throws InvalidArgumentException for invalid query strings.
      */
     public function withQuery($query)
     {
         $uri = $this->uri->withQuery($query);
-        return new Uri($uri);
+        return new static($uri);
     }
 
     /**
@@ -336,13 +336,13 @@ public function withQuery($query)
      * An empty scheme is equivalent to removing the scheme.
      *
      * @param string $scheme The scheme to use with the new instance.
-     * @return Uri A new instance with the specified scheme.
+     * @return static A new instance with the specified scheme.
      * @throws InvalidArgumentException for invalid or unsupported schemes.
      */
     public function withScheme($scheme)
     {
         $uri = $this->uri->withScheme($scheme);
-        return new Uri($uri);
+        return new static($uri);
     }
 
     /**
@@ -357,12 +357,12 @@ public function withScheme($scheme)
      *
      * @param string $user The user name to use for authority.
      * @param null|string $password The password associated with $user.
-     * @return Uri A new instance with the specified user information.
+     * @return static A new instance with the specified user information.
      */
     public function withUserInfo($user, $password = null)
     {
         $uri = $this->uri->withUserInfo($user, $password);
-        return new Uri($uri);
+        return new static($uri);
     }
 
     /**