diff --git a/src/Http/ActionDispatcher.php b/src/Http/ActionDispatcher.php
index efb718cd626..2e4ee2011b0 100644
--- a/src/Http/ActionDispatcher.php
+++ b/src/Http/ActionDispatcher.php
@@ -64,16 +64,19 @@ public function __construct($factory = null, $eventManager = null, array $filter
             $this->addFilter($filter);
         }
         $this->factory = $factory ?: new ControllerFactory();
+
+        // Force aliases to be autoloaded.
+        class_exists('Cake\Network\Request');
     }
 
     /**
      * Dispatches a Request & Response
      *
-     * @param \Cake\Network\Request $request The request to dispatch.
+     * @param \Cake\Http\ServerRequest $request The request to dispatch.
      * @param \Cake\Network\Response $response The response to dispatch.
      * @return \Cake\Network\Response A modified/replaced response.
      */
-    public function dispatch(Request $request, Response $response)
+    public function dispatch(ServerRequest $request, Response $response)
     {
         if (Router::getRequest(true) !== $request) {
             Router::pushRequest($request);
diff --git a/src/Http/BaseApplication.php b/src/Http/BaseApplication.php
index d0301dcf2d3..bc6d0e19a0c 100644
--- a/src/Http/BaseApplication.php
+++ b/src/Http/BaseApplication.php
@@ -75,13 +75,7 @@ public function bootstrap()
      */
     public function __invoke(ServerRequestInterface $request, ResponseInterface $response, $next)
     {
-        $cakeResponse = ResponseTransformer::toCake($response);
-
-        // Dispatch the request/response to CakePHP
-        $cakeResponse = $this->getDispatcher()->dispatch($request, $cakeResponse);
-
-        // Convert the response back into a PSR7 object.
-        return ResponseTransformer::toPsr($cakeResponse);
+        return $this->getDispatcher()->dispatch($request, $response);
     }
 
     /**
diff --git a/src/Http/Server.php b/src/Http/Server.php
index 039d9fb3184..34b826c690e 100644
--- a/src/Http/Server.php
+++ b/src/Http/Server.php
@@ -15,11 +15,11 @@
 namespace Cake\Http;
 
 use Cake\Event\EventDispatcherTrait;
+use Cake\Network\Response;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use RuntimeException;
 use UnexpectedValueException;
-use Zend\Diactoros\Response;
 use Zend\Diactoros\Response\EmitterInterface;
 use Zend\Diactoros\Response\SapiEmitter;
 use Zend\Diactoros\Response\SapiStreamEmitter;
diff --git a/src/TestSuite/IntegrationTestCase.php b/src/TestSuite/IntegrationTestCase.php
index 947f07dd80d..fc77be3a756 100644
--- a/src/TestSuite/IntegrationTestCase.php
+++ b/src/TestSuite/IntegrationTestCase.php
@@ -700,16 +700,16 @@ public function assertRedirect($url = null, $message = '')
         if (!$this->_response) {
             $this->fail('No response set, cannot assert location header. ' . $message);
         }
-        $result = $this->_response->header();
+        $result = $this->_response->getHeaderLine('Location');
         if ($url === null) {
-            $this->assertTrue(!empty($result['Location']), $message);
+            $this->assertTrue(!empty($result), $message);
 
             return;
         }
-        if (empty($result['Location'])) {
+        if (empty($result)) {
             $this->fail('No location header set. ' . $message);
         }
-        $this->assertEquals(Router::url($url, ['_full' => true]), $result['Location'], $message);
+        $this->assertEquals(Router::url($url, ['_full' => true]), $result, $message);
     }
 
     /**
@@ -724,11 +724,11 @@ public function assertRedirectContains($url, $message = '')
         if (!$this->_response) {
             $this->fail('No response set, cannot assert location header. ' . $message);
         }
-        $result = $this->_response->header();
-        if (empty($result['Location'])) {
+        $result = $this->_response->getHeaderLine('Location');
+        if (empty($result)) {
             $this->fail('No location header set. ' . $message);
         }
-        $this->assertContains($url, $result['Location'], $message);
+        $this->assertContains($url, $result, $message);
     }
 
     /**
@@ -742,14 +742,14 @@ public function assertNoRedirect($message = '')
         if (!$this->_response) {
             $this->fail('No response set, cannot assert location header. ' . $message);
         }
-        $result = $this->_response->header();
+        $result = $this->_response->getHeaderLine('Location');
         if (!$message) {
             $message = 'Redirect header set';
         }
-        if (!empty($result['Location'])) {
-            $message .= ': ' . $result['Location'];
+        if (!empty($result)) {
+            $message .= ': ' . $result;
         }
-        $this->assertTrue(empty($result['Location']), $message);
+        $this->assertTrue(empty($result), $message);
     }
 
     /**
@@ -765,11 +765,11 @@ public function assertHeader($header, $content, $message = '')
         if (!$this->_response) {
             $this->fail('No response set, cannot assert headers. ' . $message);
         }
-        $headers = $this->_response->header();
-        if (!isset($headers[$header])) {
+        if (!$this->_response->hasHeader($header)) {
             $this->fail("The '$header' header is not set. " . $message);
         }
-        $this->assertEquals($headers[$header], $content, $message);
+        $actual = $this->_response->getHeaderLine($header);
+        $this->assertEquals($content, $actual, $message);
     }
 
     /**
@@ -785,11 +785,11 @@ public function assertHeaderContains($header, $content, $message = '')
         if (!$this->_response) {
             $this->fail('No response set, cannot assert headers. ' . $message);
         }
-        $headers = $this->_response->header();
-        if (!isset($headers[$header])) {
+        if (!$this->_response->hasHeader($header)) {
             $this->fail("The '$header' header is not set. " . $message);
         }
-        $this->assertContains($content, $headers[$header], $message);
+        $actual = $this->_response->getHeaderLine($header);
+        $this->assertContains($content, $actual, $message);
     }
 
     /**
diff --git a/src/TestSuite/MiddlewareDispatcher.php b/src/TestSuite/MiddlewareDispatcher.php
index 44d229e77b6..4f132c96ca6 100644
--- a/src/TestSuite/MiddlewareDispatcher.php
+++ b/src/TestSuite/MiddlewareDispatcher.php
@@ -94,9 +94,7 @@ public function execute($request)
 
         $server = new Server($app);
         $psrRequest = $this->_createRequest($request);
-        $response = $server->run($psrRequest);
-
-        return ResponseTransformer::toCake($response);
+        return $server->run($psrRequest);
     }
 
     /**
diff --git a/tests/TestCase/Http/BaseApplicationTest.php b/tests/TestCase/Http/BaseApplicationTest.php
index 1ca39018b3f..11dad5423dd 100644
--- a/tests/TestCase/Http/BaseApplicationTest.php
+++ b/tests/TestCase/Http/BaseApplicationTest.php
@@ -4,8 +4,8 @@
 use Cake\Core\Configure;
 use Cake\Http\BaseApplication;
 use Cake\Http\ServerRequestFactory;
+use Cake\Network\Response;
 use Cake\TestSuite\TestCase;
-use Zend\Diactoros\Response;
 
 /**
  * Base application test.