diff --git a/composer.json b/composer.json
index 56e8c0a..c66e5ab 100644
--- a/composer.json
+++ b/composer.json
@@ -7,7 +7,7 @@
     "authors": [
         {
             "name": "PHP-FIG",
-            "homepage": "http://www.php-fig.org/"
+            "homepage": "https://www.php-fig.org/"
         }
     ],
     "require": {
@@ -20,7 +20,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "1.1.x-dev"
+            "dev-master": "2.0.x-dev"
         }
     }
 }
diff --git a/src/MessageInterface.php b/src/MessageInterface.php
index 8cdb4ed..a83c985 100644
--- a/src/MessageInterface.php
+++ b/src/MessageInterface.php
@@ -1,7 +1,5 @@
 <?php
 
-declare(strict_types=1);
-
 namespace Psr\Http\Message;
 
 /**
@@ -25,7 +23,7 @@ interface MessageInterface
      *
      * @return string HTTP protocol version.
      */
-    public function getProtocolVersion();
+    public function getProtocolVersion(): string;
 
     /**
      * Return an instance with the specified HTTP protocol version.
@@ -40,7 +38,7 @@ public function getProtocolVersion();
      * @param string $version HTTP protocol version
      * @return static
      */
-    public function withProtocolVersion(string $version);
+    public function withProtocolVersion(string $version): MessageInterface;
 
     /**
      * Retrieves all message header values.
@@ -67,7 +65,7 @@ public function withProtocolVersion(string $version);
      *     key MUST be a header name, and each value MUST be an array of strings
      *     for that header.
      */
-    public function getHeaders();
+    public function getHeaders(): array;
 
     /**
      * Checks if a header exists by the given case-insensitive name.
@@ -77,7 +75,7 @@ public function getHeaders();
      *     name using a case-insensitive string comparison. Returns false if
      *     no matching header name is found in the message.
      */
-    public function hasHeader(string $name);
+    public function hasHeader(string $name): bool;
 
     /**
      * Retrieves a message header value by the given case-insensitive name.
@@ -93,7 +91,7 @@ public function hasHeader(string $name);
      *    header. If the header does not appear in the message, this method MUST
      *    return an empty array.
      */
-    public function getHeader(string $name);
+    public function getHeader(string $name): array;
 
     /**
      * Retrieves a comma-separated string of the values for a single header.
@@ -114,7 +112,7 @@ public function getHeader(string $name);
      *    concatenated together using a comma. If the header does not appear in
      *    the message, this method MUST return an empty string.
      */
-    public function getHeaderLine(string $name);
+    public function getHeaderLine(string $name): string;
 
     /**
      * Return an instance with the provided value replacing the specified header.
@@ -131,7 +129,7 @@ public function getHeaderLine(string $name);
      * @return static
      * @throws \InvalidArgumentException for invalid header names or values.
      */
-    public function withHeader(string $name, $value);
+    public function withHeader(string $name, $value): MessageInterface;
 
     /**
      * Return an instance with the specified header appended with the given value.
@@ -149,7 +147,7 @@ public function withHeader(string $name, $value);
      * @return static
      * @throws \InvalidArgumentException for invalid header names or values.
      */
-    public function withAddedHeader(string $name, $value);
+    public function withAddedHeader(string $name, $value): MessageInterface;
 
     /**
      * Return an instance without the specified header.
@@ -163,14 +161,14 @@ public function withAddedHeader(string $name, $value);
      * @param string $name Case-insensitive header field name to remove.
      * @return static
      */
-    public function withoutHeader(string $name);
+    public function withoutHeader(string $name): MessageInterface;
 
     /**
      * Gets the body of the message.
      *
      * @return StreamInterface Returns the body as a stream.
      */
-    public function getBody();
+    public function getBody(): StreamInterface;
 
     /**
      * Return an instance with the specified message body.
@@ -185,5 +183,5 @@ public function getBody();
      * @return static
      * @throws \InvalidArgumentException When the body is not valid.
      */
-    public function withBody(StreamInterface $body);
+    public function withBody(StreamInterface $body): MessageInterface;
 }
diff --git a/src/RequestInterface.php b/src/RequestInterface.php
index 38066df..33f85e5 100644
--- a/src/RequestInterface.php
+++ b/src/RequestInterface.php
@@ -1,7 +1,5 @@
 <?php
 
-declare(strict_types=1);
-
 namespace Psr\Http\Message;
 
 /**
@@ -41,7 +39,7 @@ interface RequestInterface extends MessageInterface
      *
      * @return string
      */
-    public function getRequestTarget();
+    public function getRequestTarget(): string;
 
     /**
      * Return an instance with the specific request-target.
@@ -60,14 +58,15 @@ public function getRequestTarget();
      * @param string $requestTarget
      * @return static
      */
-    public function withRequestTarget(string $requestTarget);
+    public function withRequestTarget(string $requestTarget): RequestInterface;
+
 
     /**
      * Retrieves the HTTP method of the request.
      *
      * @return string Returns the request method.
      */
-    public function getMethod();
+    public function getMethod(): string;
 
     /**
      * Return an instance with the provided HTTP method.
@@ -84,7 +83,7 @@ public function getMethod();
      * @return static
      * @throws \InvalidArgumentException for invalid HTTP methods.
      */
-    public function withMethod(string $method);
+    public function withMethod(string $method): RequestInterface;
 
     /**
      * Retrieves the URI instance.
@@ -95,7 +94,7 @@ public function withMethod(string $method);
      * @return UriInterface Returns a UriInterface instance
      *     representing the URI of the request.
      */
-    public function getUri();
+    public function getUri(): UriInterface;
 
     /**
      * Returns an instance with the provided URI.
@@ -127,5 +126,5 @@ public function getUri();
      * @param bool $preserveHost Preserve the original state of the Host header.
      * @return static
      */
-    public function withUri(UriInterface $uri, bool $preserveHost = false);
+    public function withUri(UriInterface $uri, bool $preserveHost = false): RequestInterface;
 }
diff --git a/src/ResponseInterface.php b/src/ResponseInterface.php
index f85ca48..e9299a9 100644
--- a/src/ResponseInterface.php
+++ b/src/ResponseInterface.php
@@ -1,7 +1,5 @@
 <?php
 
-declare(strict_types=1);
-
 namespace Psr\Http\Message;
 
 /**
@@ -29,7 +27,7 @@ interface ResponseInterface extends MessageInterface
      *
      * @return int Status code.
      */
-    public function getStatusCode();
+    public function getStatusCode(): int;
 
     /**
      * Return an instance with the specified status code and, optionally, reason phrase.
@@ -51,7 +49,7 @@ public function getStatusCode();
      * @return static
      * @throws \InvalidArgumentException For invalid status code arguments.
      */
-    public function withStatus(int $code, string $reasonPhrase = '');
+    public function withStatus(int $code, string $reasonPhrase = ''): ResponseInterface;
 
     /**
      * Gets the response reason phrase associated with the status code.
@@ -66,5 +64,5 @@ public function withStatus(int $code, string $reasonPhrase = '');
      * @link http://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
      * @return string Reason phrase; must return an empty string if none present.
      */
-    public function getReasonPhrase();
+    public function getReasonPhrase(): string;
 }
diff --git a/src/ServerRequestInterface.php b/src/ServerRequestInterface.php
index 5e6d964..8625d0e 100644
--- a/src/ServerRequestInterface.php
+++ b/src/ServerRequestInterface.php
@@ -1,7 +1,5 @@
 <?php
 
-declare(strict_types=1);
-
 namespace Psr\Http\Message;
 
 /**
@@ -53,7 +51,7 @@ interface ServerRequestInterface extends RequestInterface
      *
      * @return array
      */
-    public function getServerParams();
+    public function getServerParams(): array;
 
     /**
      * Retrieve cookies.
@@ -65,7 +63,7 @@ public function getServerParams();
      *
      * @return array
      */
-    public function getCookieParams();
+    public function getCookieParams(): array;
 
     /**
      * Return an instance with the specified cookies.
@@ -84,7 +82,7 @@ public function getCookieParams();
      * @param array $cookies Array of key/value pairs representing cookies.
      * @return static
      */
-    public function withCookieParams(array $cookies);
+    public function withCookieParams(array $cookies): ServerRequestInterface;
 
     /**
      * Retrieve query string arguments.
@@ -98,7 +96,7 @@ public function withCookieParams(array $cookies);
      *
      * @return array
      */
-    public function getQueryParams();
+    public function getQueryParams(): array;
 
     /**
      * Return an instance with the specified query string arguments.
@@ -122,7 +120,7 @@ public function getQueryParams();
      *     $_GET.
      * @return static
      */
-    public function withQueryParams(array $query);
+    public function withQueryParams(array $query): ServerRequestInterface;
 
     /**
      * Retrieve normalized file upload data.
@@ -136,7 +134,7 @@ public function withQueryParams(array $query);
      * @return array An array tree of UploadedFileInterface instances; an empty
      *     array MUST be returned if no data is present.
      */
-    public function getUploadedFiles();
+    public function getUploadedFiles(): array;
 
     /**
      * Create a new instance with the specified uploaded files.
@@ -149,7 +147,7 @@ public function getUploadedFiles();
      * @return static
      * @throws \InvalidArgumentException if an invalid structure is provided.
      */
-    public function withUploadedFiles(array $uploadedFiles);
+    public function withUploadedFiles(array $uploadedFiles): ServerRequestInterface;
 
     /**
      * Retrieve any parameters provided in the request body.
@@ -196,7 +194,7 @@ public function getParsedBody();
      * @throws \InvalidArgumentException if an unsupported argument type is
      *     provided.
      */
-    public function withParsedBody($data);
+    public function withParsedBody($data): ServerRequestInterface;
 
     /**
      * Retrieve attributes derived from the request.
@@ -209,7 +207,7 @@ public function withParsedBody($data);
      *
      * @return array Attributes derived from the request.
      */
-    public function getAttributes();
+    public function getAttributes(): array;
 
     /**
      * Retrieve a single derived request attribute.
@@ -243,7 +241,7 @@ public function getAttribute(string $name, $default = null);
      * @param mixed $value The value of the attribute.
      * @return static
      */
-    public function withAttribute(string $name, $value);
+    public function withAttribute(string $name, $value): ServerRequestInterface;
 
     /**
      * Return an instance that removes the specified derived request attribute.
@@ -259,5 +257,5 @@ public function withAttribute(string $name, $value);
      * @param string $name The attribute name.
      * @return static
      */
-    public function withoutAttribute(string $name);
+    public function withoutAttribute(string $name): ServerRequestInterface;
 }
diff --git a/src/StreamInterface.php b/src/StreamInterface.php
index 5924663..a62aabb 100644
--- a/src/StreamInterface.php
+++ b/src/StreamInterface.php
@@ -1,7 +1,5 @@
 <?php
 
-declare(strict_types=1);
-
 namespace Psr\Http\Message;
 
 /**
@@ -27,14 +25,14 @@ interface StreamInterface
      * @see http://php.net/manual/en/language.oop5.magic.php#object.tostring
      * @return string
      */
-    public function __toString();
+    public function __toString(): string;
 
     /**
      * Closes the stream and any underlying resources.
      *
      * @return void
      */
-    public function close();
+    public function close(): void;
 
     /**
      * Separates any underlying resources from the stream.
@@ -50,7 +48,7 @@ public function detach();
      *
      * @return int|null Returns the size in bytes if known, or null if unknown.
      */
-    public function getSize();
+    public function getSize(): ?int;
 
     /**
      * Returns the current position of the file read/write pointer
@@ -58,21 +56,21 @@ public function getSize();
      * @return int Position of the file pointer
      * @throws \RuntimeException on error.
      */
-    public function tell();
+    public function tell(): int;
 
     /**
      * Returns true if the stream is at the end of the stream.
      *
      * @return bool
      */
-    public function eof();
+    public function eof(): bool;
 
     /**
      * Returns whether or not the stream is seekable.
      *
      * @return bool
      */
-    public function isSeekable();
+    public function isSeekable(): bool;
 
     /**
      * Seek to a position in the stream.
@@ -86,7 +84,7 @@ public function isSeekable();
      *     SEEK_END: Set position to end-of-stream plus offset.
      * @throws \RuntimeException on failure.
      */
-    public function seek(int $offset, int $whence = SEEK_SET);
+    public function seek(int $offset, int $whence = SEEK_SET): void;
 
     /**
      * Seek to the beginning of the stream.
@@ -98,14 +96,14 @@ public function seek(int $offset, int $whence = SEEK_SET);
      * @link http://www.php.net/manual/en/function.fseek.php
      * @throws \RuntimeException on failure.
      */
-    public function rewind();
+    public function rewind(): void;
 
     /**
      * Returns whether or not the stream is writable.
      *
      * @return bool
      */
-    public function isWritable();
+    public function isWritable(): bool;
 
     /**
      * Write data to the stream.
@@ -114,14 +112,14 @@ public function isWritable();
      * @return int Returns the number of bytes written to the stream.
      * @throws \RuntimeException on failure.
      */
-    public function write(string $string);
+    public function write(string $string): int;
 
     /**
      * Returns whether or not the stream is readable.
      *
      * @return bool
      */
-    public function isReadable();
+    public function isReadable(): bool;
 
     /**
      * Read data from the stream.
@@ -133,7 +131,7 @@ public function isReadable();
      *     if no bytes are available.
      * @throws \RuntimeException if an error occurs.
      */
-    public function read(int $length);
+    public function read(int $length): string;
 
     /**
      * Returns the remaining contents in a string
@@ -142,7 +140,7 @@ public function read(int $length);
      * @throws \RuntimeException if unable to read or an error occurs while
      *     reading.
      */
-    public function getContents();
+    public function getContents(): string;
 
     /**
      * Get stream metadata as an associative array or retrieve a specific key.
diff --git a/src/UploadedFileInterface.php b/src/UploadedFileInterface.php
index aba6321..dd19d65 100644
--- a/src/UploadedFileInterface.php
+++ b/src/UploadedFileInterface.php
@@ -1,7 +1,5 @@
 <?php
 
-declare(strict_types=1);
-
 namespace Psr\Http\Message;
 
 /**
@@ -30,7 +28,7 @@ interface UploadedFileInterface
      * @throws \RuntimeException in cases when no stream is available or can be
      *     created.
      */
-    public function getStream();
+    public function getStream(): StreamInterface;
 
     /**
      * Move the uploaded file to a new location.
@@ -64,7 +62,7 @@ public function getStream();
      * @throws \RuntimeException on any error during the move operation, or on
      *     the second or subsequent call to the method.
      */
-    public function moveTo(string $targetPath);
+    public function moveTo(string $targetPath): void;
     
     /**
      * Retrieve the file size.
@@ -75,7 +73,7 @@ public function moveTo(string $targetPath);
      *
      * @return int|null The file size in bytes or null if unknown.
      */
-    public function getSize();
+    public function getSize(): ?int;
     
     /**
      * Retrieve the error associated with the uploaded file.
@@ -91,7 +89,7 @@ public function getSize();
      * @see http://php.net/manual/en/features.file-upload.errors.php
      * @return int One of PHP's UPLOAD_ERR_XXX constants.
      */
-    public function getError();
+    public function getError(): int;
     
     /**
      * Retrieve the filename sent by the client.
@@ -106,7 +104,7 @@ public function getError();
      * @return string|null The filename sent by the client or null if none
      *     was provided.
      */
-    public function getClientFilename();
+    public function getClientFilename(): ?string;
     
     /**
      * Retrieve the media type sent by the client.
@@ -121,5 +119,5 @@ public function getClientFilename();
      * @return string|null The media type sent by the client or null if none
      *     was provided.
      */
-    public function getClientMediaType();
+    public function getClientMediaType(): ?string;
 }
diff --git a/src/UriInterface.php b/src/UriInterface.php
index d974de0..15e2cf2 100644
--- a/src/UriInterface.php
+++ b/src/UriInterface.php
@@ -1,7 +1,5 @@
 <?php
 
-declare(strict_types=1);
-
 namespace Psr\Http\Message;
 
 /**
@@ -40,7 +38,7 @@ interface UriInterface
      * @see https://tools.ietf.org/html/rfc3986#section-3.1
      * @return string The URI scheme.
      */
-    public function getScheme();
+    public function getScheme(): string;
 
     /**
      * Retrieve the authority component of the URI.
@@ -60,7 +58,7 @@ public function getScheme();
      * @see https://tools.ietf.org/html/rfc3986#section-3.2
      * @return string The URI authority, in "[user-info@]host[:port]" format.
      */
-    public function getAuthority();
+    public function getAuthority(): string;
 
     /**
      * Retrieve the user information component of the URI.
@@ -77,7 +75,7 @@ public function getAuthority();
      *
      * @return string The URI user information, in "username[:password]" format.
      */
-    public function getUserInfo();
+    public function getUserInfo(): string;
 
     /**
      * Retrieve the host component of the URI.
@@ -90,7 +88,7 @@ public function getUserInfo();
      * @see http://tools.ietf.org/html/rfc3986#section-3.2.2
      * @return string The URI host.
      */
-    public function getHost();
+    public function getHost(): string;
 
     /**
      * Retrieve the port component of the URI.
@@ -107,7 +105,7 @@ public function getHost();
      *
      * @return null|int The URI port.
      */
-    public function getPort();
+    public function getPort(): ?int;
 
     /**
      * Retrieve the path component of the URI.
@@ -134,7 +132,7 @@ public function getPort();
      * @see https://tools.ietf.org/html/rfc3986#section-3.3
      * @return string The URI path.
      */
-    public function getPath();
+    public function getPath(): string;
 
     /**
      * Retrieve the query string of the URI.
@@ -156,7 +154,7 @@ public function getPath();
      * @see https://tools.ietf.org/html/rfc3986#section-3.4
      * @return string The URI query string.
      */
-    public function getQuery();
+    public function getQuery(): string;
 
     /**
      * Retrieve the fragment component of the URI.
@@ -174,7 +172,7 @@ public function getQuery();
      * @see https://tools.ietf.org/html/rfc3986#section-3.5
      * @return string The URI fragment.
      */
-    public function getFragment();
+    public function getFragment(): string;
 
     /**
      * Return an instance with the specified scheme.
@@ -191,7 +189,7 @@ public function getFragment();
      * @return static A new instance with the specified scheme.
      * @throws \InvalidArgumentException for invalid or unsupported schemes.
      */
-    public function withScheme(string $scheme);
+    public function withScheme(string $scheme): UriInterface;
 
     /**
      * Return an instance with the specified user information.
@@ -207,7 +205,7 @@ public function withScheme(string $scheme);
      * @param null|string $password The password associated with $user.
      * @return static A new instance with the specified user information.
      */
-    public function withUserInfo(string $user, ?string $password = null);
+    public function withUserInfo(string $user, ?string $password = null): UriInterface;
 
     /**
      * Return an instance with the specified host.
@@ -221,7 +219,7 @@ public function withUserInfo(string $user, ?string $password = null);
      * @return static A new instance with the specified host.
      * @throws \InvalidArgumentException for invalid hostnames.
      */
-    public function withHost(string $host);
+    public function withHost(string $host): UriInterface;
 
     /**
      * Return an instance with the specified port.
@@ -240,7 +238,7 @@ public function withHost(string $host);
      * @return static A new instance with the specified port.
      * @throws \InvalidArgumentException for invalid ports.
      */
-    public function withPort(?int $port);
+    public function withPort(?int $port): UriInterface;
 
     /**
      * Return an instance with the specified path.
@@ -264,7 +262,7 @@ public function withPort(?int $port);
      * @return static A new instance with the specified path.
      * @throws \InvalidArgumentException for invalid paths.
      */
-    public function withPath(string $path);
+    public function withPath(string $path): UriInterface;
 
     /**
      * Return an instance with the specified query string.
@@ -281,7 +279,7 @@ public function withPath(string $path);
      * @return static A new instance with the specified query string.
      * @throws \InvalidArgumentException for invalid query strings.
      */
-    public function withQuery(string $query);
+    public function withQuery(string $query): UriInterface;
 
     /**
      * Return an instance with the specified URI fragment.
@@ -297,7 +295,7 @@ public function withQuery(string $query);
      * @param string $fragment The fragment to use with the new instance.
      * @return static A new instance with the specified fragment.
      */
-    public function withFragment(string $fragment);
+    public function withFragment(string $fragment): UriInterface;
 
     /**
      * Return the string representation as a URI reference.
@@ -322,5 +320,5 @@ public function withFragment(string $fragment);
      * @see http://tools.ietf.org/html/rfc3986#section-4.1
      * @return string
      */
-    public function __toString();
+    public function __toString(): string;
 }