diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4abbb0f..d2ecab2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,19 +2,29 @@
 
 All notable changes to this project will be documented in this file, in reverse chronological order by release..
 
-## TBD - TBD
+## 0.6.0 - 2014-10.17
+
+Updated component to psr/http-message 0.4.0. That release contains a number of backwards-incompatible changes.
 
 ### Added
 
-- Nothing.
+- Added IncomingRequestFactory::setHeaders() for simplifying setting
+  (overwriting) many headers at once from an array.
+- Updated MessageTrait::addHeader() to allow array values
+- Modified IncomingRequest to `s/PathParams/Attributes/g`
 
 ### Deprecated
 
-- Nothing.
+- IncomingRequest now only allows arrays for either input or return values; Array-like objects are no longer accepted.
+- Removed ability to pass objects to MessageTrait::addHeader()/setHeader()
+- Removed setHeaders()/addHeaders() from MessageTrait
+- Modified IncomingRequest to `s/PathParams/Attributes/g`
 
 ### Removed
 
-- Nothing.
+- Removed ability to pass objects to MessageTrait::addHeader()/setHeader()
+- Removed setHeaders()/addHeaders() from MessageTrait
+- Modified IncomingRequest to `s/PathParams/Attributes/g`
 
 ### Fixed
 
diff --git a/composer.json b/composer.json
index 297dfec..992539f 100644
--- a/composer.json
+++ b/composer.json
@@ -26,7 +26,7 @@
   },
   "require": {
     "php": ">=5.4.8",
-    "psr/http-message": "~0.3.0"
+    "psr/http-message": "~0.4.0"
   },
   "require-dev": {
     "phpunit/PHPUnit": "3.7.*",
diff --git a/src/IncomingRequest.php b/src/IncomingRequest.php
index da271c7..44fdc19 100644
--- a/src/IncomingRequest.php
+++ b/src/IncomingRequest.php
@@ -1,7 +1,6 @@
 <?php
 namespace Phly\Http;
 
-use ArrayAccess;
 use InvalidArgumentException;
 use Psr\Http\Message\IncomingRequestInterface;
 
@@ -25,54 +24,55 @@
 class IncomingRequest extends Request implements IncomingRequestInterface
 {
     /**
-     * @var array|object
+     * @var array
      */
-    private $bodyParams = [];
+    private $attributes = [];
 
     /**
-     * @var array|ArrayAccess
+     * @var array
      */
-    private $cookieParams;
+    private $bodyParams = [];
 
     /**
-     * @var array|ArrayAccess
+     * @var array
      */
-    private $fileParams;
+    private $cookieParams;
 
     /**
-     * @var array|ArrayAccess
+     * @var array
      */
-    private $pathParams = [];
+    private $fileParams;
 
     /**
-     * @var array|ArrayAccess
+     * @var array
      */
     private $queryParams;
 
     /**
-     * @param string|\Psr\Http\Message\StreamableInterface|array $stream Stream representing message body.
-     *        Alternately, this can be an array with keys for each of the possible arguments.
-     * @param array|ArrayAccess $cookieParams Deserialized cookies
-     * @param array|ArrayAccess $pathParams Variables matched from the URI path
-     * @param array|ArrayAccess $queryParams Deserialized query string arguments
-     * @param array|ArrayAccess $bodyParams Deserialized body parameters
-     * @param array|ArrayAccess $fileParams Upload file information; should be in PHP's $_FILES format
+     * @param string|\Psr\Http\Message\StreamableInterface|array $stream
+     *     Stream representing message body. Alternately, this can be an 
+     *     array with keys for each of the possible arguments.
+     * @param array $cookieParams Deserialized cookies
+     * @param array $attributes Attributes derived from the request
+     * @param array $queryParams Deserialized query string arguments
+     * @param array $bodyParams Deserialized body parameters
+     * @param array $fileParams Upload file information; should be in PHP's $_FILES format
      * @return void
      */
     public function __construct(
         $stream = 'php://input',
-        $cookieParams = [],
-        $pathParams = [],
-        $queryParams = [],
-        $bodyParams = [],
-        $fileParams = []
+        array $cookieParams = [],
+        array $attributes = [],
+        array $queryParams = [],
+        array $bodyParams = [],
+        array $fileParams = []
     ) {
         if (is_array($stream)) {
             if (isset($stream['cookieParams']) && empty($cookieParams)) {
                 $cookieParams = $stream['cookieParams'];
             }
-            if (isset($stream['pathParams']) && empty($pathParams)) {
-                $pathParams = $stream['pathParams'];
+            if (isset($stream['attributes']) && empty($attributes)) {
+                $attributes = $stream['attributes'];
             }
             if (isset($stream['queryParams']) && empty($queryParams)) {
                 $queryParams = $stream['queryParams'];
@@ -89,7 +89,7 @@ public function __construct(
 
         parent::__construct($stream);
         $this->setCookieParams($cookieParams);
-        $this->setPathParams($pathParams);
+        $this->setAttributes($attributes);
         $this->setQueryParams($queryParams);
         $this->setBodyParams($bodyParams);
         $this->setFileParams($fileParams);
@@ -100,14 +100,7 @@ public function __construct(
      *
      * Retrieves cookies sent by the client to the server.
      *
-     * The assumption is these are injected during instantiation, typically
-     * from PHP's $_COOKIE superglobal, and should remain immutable over the
-     * course of the incoming request.
-     *
-     * The return value can be either an array or an object that acts like
-     * an array (e.g., implements ArrayAccess, or an ArrayObject).
-     * 
-     * @return array|ArrayAccess
+     * @return array
      */
     public function getCookieParams()
     {
@@ -123,21 +116,10 @@ public function getCookieParams()
      * the original value, filter them, and re-inject into the incoming
      * request..
      *
-     * The value provided should be an array or array-like object
-     * (e.g., implements ArrayAccess, or an ArrayObject).
-     * 
-     * @param array|ArrayAccess $cookies Cookie values/structs
-     * 
-     * @return void
+     * @param array $cookies Cookie values/structs
      */
-    public function setCookieParams($cookies)
+    public function setCookieParams(array $cookies)
     {
-        if (! is_array($cookies) && ! $cookies instanceof ArrayAccess) {
-            throw new InvalidArgumentException(
-                'Cookies must be provided as either an array or ArrayAccess'
-            );
-        }
-
         $this->cookieParams = $cookies;
     }
 
@@ -150,10 +132,7 @@ public function setCookieParams($cookies)
      * from PHP's $_GET superglobal, and should remain immutable over the
      * course of the incoming request.
      *
-     * The return value can be either an array or an object that acts like
-     * an array (e.g., implements ArrayAccess, or an ArrayObject).
-     * 
-     * @return array|ArrayAccess
+     * @return array
      */
     public function getQueryParams()
     {
@@ -165,16 +144,10 @@ public function getQueryParams()
      *
      * Internal method only.
      * 
-     * @param array|ArrayAccess $queryParams 
+     * @param array $queryParams 
      */
-    private function setQueryParams($queryParams)
+    private function setQueryParams(array $queryParams)
     {
-        if (! is_array($queryParams) && ! $queryParams instanceof ArrayAccess) {
-            throw new InvalidArgumentException(
-                'Query string arguments must be provided as either an array or ArrayAccess'
-            );
-        }
-
         $this->queryParams = $queryParams;
     }
 
@@ -188,10 +161,7 @@ private function setQueryParams($queryParams)
      * from PHP's $_FILES superglobal, and should remain immutable over the
      * course of the incoming request.
      *
-     * The return value can be either an array or an object that acts like
-     * an array (e.g., implements ArrayAccess, or an ArrayObject).
-     * 
-     * @return array|ArrayAccess Upload file(s) metadata, if any.
+     * @return array Upload file(s) metadata, if any.
      */
     public function getFileParams()
     {
@@ -203,16 +173,10 @@ public function getFileParams()
      *
      * Internal method only.
      * 
-     * @param array|ArrayAccess $fileParams 
+     * @param array $fileParams 
      */
-    private function setFileParams($fileParams)
+    private function setFileParams(array $fileParams)
     {
-        if (! is_array($fileParams) && ! $fileParams instanceof ArrayAccess) {
-            throw new InvalidArgumentException(
-                'Files must be provided as either an array or ArrayAccess'
-            );
-        }
-
         $this->fileParams = $fileParams;
     }
 
@@ -220,15 +184,13 @@ private function setFileParams($fileParams)
      * Retrieve any parameters provided in the request body.
      *
      * If the request body can be deserialized, and if the deserialized values
-     * can be represented as an array or object, this method can be used to
+     * can be represented as an array, this method can be used to
      * retrieve them.
      *
      * In other cases, the parent getBody() method should be used to retrieve
      * the body content.
      * 
-     * @return array|object The deserialized body parameters, if any. These may
-     *                      be either an array or an object, though an array or
-     *                      array-like object is recommended.
+     * @return array The deserialized body parameters, if any.
      */
     public function getBodyParams()
     {
@@ -238,61 +200,42 @@ public function getBodyParams()
     /**
      * Set the request body parameters.
      *
-     * If the body content can be deserialized, the values obtained may then
+     * If the body content can be deserialized as an array, the values obtained may then
      * be injected into the response using this method. This method will
      * typically be invoked by a factory marshaling request parameters.
      * 
-     * @param array|object $values The deserialized body parameters, if any.
-     *                             These may be either an array or an object,
-     *                             though an array or array-like object is
-     *                             recommended.
-     *
-     * @return void
+     * @param array $values The deserialized body parameters, if any.
      */
-    public function setBodyParams($values)
+    public function setBodyParams(array $values)
     {
-        if (! is_array($values) && ! is_object($values)) {
-            throw new InvalidArgumentException(
-                'Body parameters must be provided as either an array or an object'
-            );
-        }
-
         $this->bodyParams = $values;
     }
 
     /**
-     * Retrieve parameters matched during routing.
+     * Retrieve attributes derived from the request
      *
      * If a router or similar is used to match against the path and/or request,
      * this method can be used to retrieve the results, so long as those
-     * results can be represented as an array or array-like object.
+     * results can be represented as an array.
      *
-     * @return array|ArrayAccess Path parameters matched by routing
+     * @return array Path parameters matched by routing
      */
-    public function getPathParams()
+    public function getAttributes()
     {
-        return $this->pathParams;
+        return $this->attributes;
     }
 
     /**
      * Set parameters discovered by matching that path
      *
      * If a router or similar is used to match against the path and/or request,
-     * this method can be used to inject the request with the results, so long
-     * as those results can be represented as an array or array-like object.
+     * this method can be used to inject them, so long as those
+     * results can be represented as an array.
      * 
-     * @param array|ArrayAccess $values Path parameters matched by routing
-     *
-     * @return void
+     * @param array $values Path parameters matched by routing
      */
-    public function setPathParams(array $values)
+    public function setAttributes(array $values)
     {
-        if (! is_array($values) && ! $values instanceof ArrayAccess) {
-            throw new InvalidArgumentException(
-                'Path parameters must be provided as either an array or ArrayAccess'
-            );
-        }
-
-        $this->pathParams = $values;
+        $this->attributes = $values;
     }
 }
diff --git a/src/IncomingRequestFactory.php b/src/IncomingRequestFactory.php
index 64855be..2d05c9d 100644
--- a/src/IncomingRequestFactory.php
+++ b/src/IncomingRequestFactory.php
@@ -2,6 +2,7 @@
 namespace Phly\Http;
 
 use Psr\Http\Message\IncomingRequestInterface;
+use Psr\Http\Message\RequestInterface;
 use stdClass;
 
 /**
@@ -72,7 +73,7 @@ public static function fromServer(array $server, IncomingRequestInterface $reque
         }
 
         $request->setMethod(self::get('REQUEST_METHOD', $server, 'GET'));
-        $request->setHeaders(self::marshalHeaders($server));
+        self::setHeaders($request, self::marshalHeaders($server));
         $request->setUrl(self::marshalUri($server, $request));
         return $request;
     }
@@ -157,6 +158,21 @@ public static function marshalHeaders(array $server)
         return $headers;
     }
 
+    /**
+     * Set the headers for a request.
+     *
+     * Injects the given request instance with the headers provided.
+     * 
+     * @param RequestInterface $request 
+     * @param array $headers 
+     */
+    public static function setHeaders(RequestInterface $request, array $headers)
+    {
+        foreach ($headers as $header => $values) {
+            $request->setHeader($header, $values);
+        }
+    }
+
     /**
      * Marshal the URI from the $_SERVER array and headers
      *
diff --git a/src/MessageTrait.php b/src/MessageTrait.php
index dd96e76..d444357 100644
--- a/src/MessageTrait.php
+++ b/src/MessageTrait.php
@@ -6,7 +6,7 @@
 
 /**
  * Trait implementing the various methods defined in
- * \Psr\Http\Message\ MessageInterface.
+ * \Psr\Http\Message\MessageInterface.
  */
 trait MessageTrait
 {
@@ -155,65 +155,23 @@ public function getHeaderAsArray($header)
      * or an array of strings.
      *
      * @param string $header Header name
-     * @param string|string[]|object|object[] $value  Header values; any objects must be castable to strings
-     *
-     * @return void
+     * @param string|string[] $value  Header value(s)
      */
     public function setHeader($header, $value)
     {
-        if (is_object($value) && method_exists($value, '__toString')) {
-            $value = (string) $value;
-        }
-
-        if (! is_string($value) && ! is_array($value)) {
-            throw new InvalidArgumentException('Invalid header value; must be a string or array of strings');
-        }
-
-        if (is_array($value)) {
-            $valid = true;
-            array_walk($value, function ($value) use (&$valid) {
-                if (is_object($value) && method_exists($value, '__toString')) {
-                    $value = (string) $value;
-                }
-
-                if (! is_string($value)) {
-                    $valid = false;
-                }
-            });
-
-            if (! $valid) {
-                throw new InvalidArgumentException('Invalid header value; must be a string or array of strings');
-            }
-        }
+        $header = strtolower($header);
 
         if (is_string($value)) {
-            $value = [$value];
+            $value = [ $value ];
         }
 
-        $this->headers[strtolower($header)] = $value;
-    }
-
-    /**
-     * Sets headers, replacing any headers that have already been set on the message.
-     *
-     * The array keys MUST be a string. The array values must be either a
-     * string or an array of strings.
-     *
-     * @param array $headers Headers to set.
-     *
-     * @return void
-     */
-    public function setHeaders(array $headers)
-    {
-        $this->headers = [];
-
-        foreach ($headers as $key => $value) {
-            if (! is_string($key)) {
-                throw new InvalidArgumentException('One or more keys in the headers array is not a string');
-            }
-
-            $this->setHeader($key, $value);
+        if (! is_array($value) || ! $this->arrayContainsOnlyStrings($value)) {
+            throw new InvalidArgumentException(
+                'Invalid header value; must be a string or array of strings'
+            );
         }
+
+        $this->headers[$header] = $value;
     }
 
     /**
@@ -223,20 +181,20 @@ public function setHeaders(array $headers)
      * value will be appended to the existing list.
      *
      * @param string $header Header name to add
-     * @param string|object $value  Value of the header; if an object, must be able to cast to a string
-     *
-     * @return void
+     * @param string|string[] $value  Value of the header; a string or array of strings
      */
     public function addHeader($header, $value)
     {
         $header = strtolower($header);
 
-        if (is_object($value) && method_exists($value, '__toString')) {
-            $value = (string) $value;
+        if (is_string($value)) {
+            $value = [ $value ];
         }
 
-        if (! is_string($value)) {
-            throw new InvalidArgumentException('Invalid header value; must be a string');
+        if (! is_array($value) || ! $this->arrayContainsOnlyStrings($value)) {
+            throw new InvalidArgumentException(
+                'Invalid header value; must be a string or array of strings'
+            );
         }
 
         if (! $this->hasHeader($header)) {
@@ -244,27 +202,7 @@ public function addHeader($header, $value)
             return;
         }
 
-        $this->headers[$header][] = $value;
-    }
-
-    /**
-     * Merges in an associative array of headers.
-     *
-     * Each array key MUST be a string representing the case-insensitive name
-     * of a header. Each value MUST be either a string or an array of strings.
-     * For each value, the value is appended to any existing header of the same
-     * name, or, if a header does not already exist by the given name, then the
-     * header is added.
-     *
-     * @param array $headers Associative array of headers to add to the message
-     *
-     * @return void
-     */
-    public function addHeaders(array $headers)
-    {
-        foreach ($headers as $header => $value) {
-            $this->addHeader($header, $value);
-        }
+        $this->headers[$header] = array_merge($this->headers[$header], $value);
     }
 
     /**
@@ -282,4 +220,32 @@ public function removeHeader($header)
 
         unset($this->headers[strtolower($header)]);
     }
+
+    /**
+     * Test that an array contains only strings
+     * 
+     * @param array $array 
+     * @return bool
+     */
+    private function arrayContainsOnlyStrings(array $array)
+    {
+        return array_reduce($array, [ __CLASS__, 'filterStringValue'], true);
+    }
+
+    /**
+     * Test if a value is a string
+     *
+     * Used with array_reduce.
+     * 
+     * @param bool $carry 
+     * @param mixed $item 
+     * @return bool
+     */
+    private static function filterStringValue($carry, $item)
+    {
+        if (! is_string($item)) {
+            return false;
+        }
+        return $carry;
+    }
 }
diff --git a/test/IncomingRequestFactoryTest.php b/test/IncomingRequestFactoryTest.php
index 8042652..9991d63 100644
--- a/test/IncomingRequestFactoryTest.php
+++ b/test/IncomingRequestFactoryTest.php
@@ -403,6 +403,6 @@ public function testCanCreateIncomingRequestViaFromGlobalsMethod()
         $this->assertEquals($query, $request->getQueryParams());
         $this->assertEquals($body, $request->getBodyParams());
         $this->assertEquals($files, $request->getFileParams());
-        $this->assertEmpty($request->getPathParams());
+        $this->assertEmpty($request->getAttributes());
     }
 }
diff --git a/test/IncomingRequestTest.php b/test/IncomingRequestTest.php
index 9d38e5b..549d6ea 100644
--- a/test/IncomingRequestTest.php
+++ b/test/IncomingRequestTest.php
@@ -31,9 +31,9 @@ public function testBodyParamsAreEmptyByDefault()
         $this->assertEmpty($this->request->getBodyParams());
     }
 
-    public function testPathParamsAreEmptyByDefault()
+    public function testAttributesAreEmptyByDefault()
     {
-        $this->assertEmpty($this->request->getPathParams());
+        $this->assertEmpty($this->request->getAttributes());
     }
 
     /**
@@ -63,35 +63,35 @@ public function testBodyParamsAreMutable()
     }
 
     /**
-     * @depends testPathParamsAreEmptyByDefault
+     * @depends testAttributesAreEmptyByDefault
      */
-    public function testPathParamsAreMutable()
+    public function testAttributesAreMutable()
     {
         $params = [
             'foo' => 'bar',
             'baz' => 'bat',
         ];
-        $this->request->setPathParams($params);
-        $this->assertEquals($params, $this->request->getPathParams());
+        $this->request->setAttributes($params);
+        $this->assertEquals($params, $this->request->getAttributes());
     }
 
     public function testRequestDataMayBeSetAsDiscreteConstructorArguments()
     {
-        $cookies = $path = $query = $body = $files = [
+        $cookies = $attributes = $query = $body = $files = [
             'foo' => 'bar',
             'baz' => 'bat',
         ];
 
         $cookies['cookies'] = true;
-        $path['path']       = true;
+        $attributes['path'] = true;
         $query['query']     = true;
         $body['body']       = true;
         $files['files']     = true;
 
-        $request = new IncomingRequest('php://memory', $cookies, $path, $query, $body, $files);
+        $request = new IncomingRequest('php://memory', $cookies, $attributes, $query, $body, $files);
 
         $this->assertEquals($cookies, $request->getCookieParams());
-        $this->assertEquals($path, $request->getPathParams());
+        $this->assertEquals($attributes, $request->getAttributes());
         $this->assertEquals($query, $request->getQueryParams());
         $this->assertEquals($body, $request->getBodyParams());
         $this->assertEquals($files, $request->getFileParams());
@@ -99,13 +99,13 @@ public function testRequestDataMayBeSetAsDiscreteConstructorArguments()
 
     public function testRequestDataMayBePassedViaAnAssociativeArray()
     {
-        $cookies = $path = $query = $body = $files = [
+        $cookies = $attributes = $query = $body = $files = [
             'foo' => 'bar',
             'baz' => 'bat',
         ];
 
         $cookies['cookies'] = true;
-        $path['path']       = true;
+        $attributes['path'] = true;
         $query['query']     = true;
         $body['body']       = true;
         $files['files']     = true;
@@ -113,7 +113,7 @@ public function testRequestDataMayBePassedViaAnAssociativeArray()
         $data = [
             'stream'       => 'php://memory',
             'cookieParams' => $cookies,
-            'pathParams'   => $path,
+            'attributes'   => $attributes,
             'queryParams'  => $query,
             'bodyParams'   => $body,
             'fileParams'   => $files,
@@ -122,7 +122,7 @@ public function testRequestDataMayBePassedViaAnAssociativeArray()
         $request = new IncomingRequest($data);
 
         $this->assertEquals($cookies, $request->getCookieParams());
-        $this->assertEquals($path, $request->getPathParams());
+        $this->assertEquals($attributes, $request->getAttributes());
         $this->assertEquals($query, $request->getQueryParams());
         $this->assertEquals($body, $request->getBodyParams());
         $this->assertEquals($files, $request->getFileParams());
diff --git a/test/MessageTraitTest.php b/test/MessageTraitTest.php
index e692418..2110f3c 100644
--- a/test/MessageTraitTest.php
+++ b/test/MessageTraitTest.php
@@ -25,23 +25,6 @@ public function testBodyIsMutable()
         $this->assertSame($stream, $this->message->getBody());
     }
 
-    public function testCanSetHeaders()
-    {
-        $headers = array(
-            'Origin'        => 'http://example.com',
-            'Accept'        => 'application/json',
-            'Content-Type'  => 'application/json',
-            'Authorization' => 'Bearer foobartoken',
-        );
-
-        $this->message->setHeaders($headers);
-        $expected = array_change_key_case($headers);
-        array_walk($expected, function (&$value) {
-            $value = [$value];
-        });
-        $this->assertEquals($expected, $this->message->getHeaders());
-    }
-
     public function testGetHeaderAsArrayReturnsHeaderValueAsArray()
     {
         $this->message->setHeader('X-Foo', ['Foo', 'Bar']);
@@ -72,25 +55,6 @@ public function testAddHeaderAppendsToExistingHeader()
         $this->assertEquals('Foo,Bar', $this->message->getHeader('X-Foo'));
     }
 
-    public function testAddHeadersMergesWithExistingHeaders()
-    {
-        $headers = [
-            'Origin'        => 'http://example.com',
-            'Accept'        => 'application/json',
-            'Content-Type'  => 'application/json',
-            'Authorization' => 'Bearer foobartoken',
-        ];
-        $this->message->setHeaders($headers);
-
-        $this->message->addHeaders([
-            'Accept' => 'application/*+json',
-            'X-Foo'  => 'Foo',
-        ]);
-
-        $this->assertEquals(['application/json', 'application/*+json'], $this->message->getHeaderAsArray('accept'));
-        $this->assertEquals('Foo', $this->message->getHeader('x-foo'));
-    }
-
     public function testCanRemoveHeaders()
     {
         $this->message->setHeader('X-Foo', 'Foo');
@@ -107,7 +71,7 @@ public function invalidGeneralHeaderValues()
             'false'  => [false],
             'int'    => [1],
             'float'  => [1.1],
-            'array'  => [[ 'foo' => 'bar' ]],
+            'array'  => [[ 'foo' => [ 'bar' ] ]],
             'object' => [(object) [ 'foo' => 'bar' ]],
         ];
     }
@@ -142,19 +106,10 @@ public function testSetHeaderRaisesExceptionForInvalidValueType($value)
         $this->message->setHeader('X-Foo', $value);
     }
 
-    public function testSetHeadersRaisesExceptionForNonStringKeys()
-    {
-        $this->setExpectedException('InvalidArgumentException', 'not a string');
-        $this->message->setHeaders([
-            'application/json',
-            'text/plain',
-        ]);
-    }
-
     /**
      * @dataProvider invalidGeneralHeaderValues
      */
-    public function testAddHeaderRaisesExceptionForNonStringValue($value)
+    public function testAddHeaderRaisesExceptionForNonStringNonArrayValue($value)
     {
         $this->setExpectedException('InvalidArgumentException', 'must be a string');
         $this->message->addHeader('X-Foo', $value);
@@ -166,28 +121,4 @@ public function testRemoveHeaderDoesNothingIfHeaderDoesNotExist()
         $this->message->removeHeader('X-Foo');
         $this->assertFalse($this->message->hasHeader('X-Foo'));
     }
-
-    public function testAllowAddingHeaderValuesUsingObjectsThatCastToString()
-    {
-        $header = new TestAsset\Header();
-        $header->value = 'foo; bar; baz, bat';
-        $this->message->addHeader('X-Foo', $header);
-        $this->assertEquals((string) $header, $this->message->getHeader('X-Foo'));
-    }
-
-    public function testAllowSettingArrayOfHeaderValuesUsingObjectsThatCastToString()
-    {
-        $values = [];
-        foreach (range(1, 5) as $i) {
-            $header = new TestAsset\Header();
-            $header->value = 'foo(' . $i . ')';
-            $values[] = $header;
-        }
-        $this->message->setHeader('X-Foo', $values);
-
-        $value = $this->message->getHeader('X-Foo');
-        foreach (range(1, 5) as $i) {
-            $this->assertContains('foo(' . $i . ')', $value);
-        }
-    }
 }
diff --git a/test/ResponseTest.php b/test/ResponseTest.php
index 3fe1f82..7bb48b6 100644
--- a/test/ResponseTest.php
+++ b/test/ResponseTest.php
@@ -62,20 +62,4 @@ public function testConstructorRaisesExceptionForInvalidStream()
         $this->setExpectedException('InvalidArgumentException');
         new Response([ 'TOTALLY INVALID' ]);
     }
-
-    public function testSetHeadersDelegatesToParent()
-    {
-        $this->response->setHeaders([
-            'Content-Type' => 'application/json',
-        ]);
-        $this->assertTrue($this->response->hasHeader('Content-Type'));
-    }
-
-    public function testAddHeadersDelegatesToParent()
-    {
-        $this->response->addHeaders([
-            'Content-Type' => 'application/json',
-        ]);
-        $this->assertTrue($this->response->hasHeader('Content-Type'));
-    }
 }
diff --git a/test/TestAsset/Header.php b/test/TestAsset/Header.php
deleted file mode 100644
index 4d5400d..0000000
--- a/test/TestAsset/Header.php
+++ /dev/null
@@ -1,12 +0,0 @@
-<?php
-namespace PhlyTest\Http\TestAsset;
-
-class Header
-{
-    public $value = '';
-
-    public function __toString()
-    {
-        return $this->value;
-    }
-}