.../EventSubscriber/ResourceResponseSubscriber.php |  9 +--
 .../ResourceResponseSubscriberTest.php             | 77 ++++++++++++++++------
 2 files changed, 60 insertions(+), 26 deletions(-)

diff --git a/core/modules/rest/src/EventSubscriber/ResourceResponseSubscriber.php b/core/modules/rest/src/EventSubscriber/ResourceResponseSubscriber.php
index ce77e01..514f4ee 100644
--- a/core/modules/rest/src/EventSubscriber/ResourceResponseSubscriber.php
+++ b/core/modules/rest/src/EventSubscriber/ResourceResponseSubscriber.php
@@ -71,7 +71,7 @@ public function onRespond(FilterResponseEvent $event) {
 
     $request = $event->getRequest();
     $format = $this->getResponseFormat($this->routeMatch, $request);
-    $response = $this->renderResponseBody($request, $response, $this->serializer, $format);
+    $this->renderResponseBody($request, $response, $this->serializer, $format);
     $event->setResponse($this->flattenResponse($response));
   }
 
@@ -142,9 +142,6 @@ public function getResponseFormat(RouteMatchInterface $route_match, Request $req
    *   The response format, or NULL in case the response does not need a format,
    *   for example for the response to a DELETE request.
    *
-   * @return \Drupal\rest\ResourceResponse
-   *   The altered response.
-   *
    * @todo Add test coverage for language negotiation contexts in
    *   https://www.drupal.org/node/2135829.
    */
@@ -171,8 +168,6 @@ protected function renderResponseBody(Request $request, ResourceResponseInterfac
       $response->setContent($output);
       $response->headers->set('Content-Type', $request->getMimeType($format));
     }
-
-    return $response;
   }
 
   /**
@@ -191,6 +186,8 @@ protected function flattenResponse(ResourceResponseInterface $response) {
     $final_response = ($response instanceof CacheableResponseInterface) ? new CacheableResponse() : new Response();
     $final_response->setContent($response->getContent());
     $final_response->setStatusCode($response->getStatusCode());
+    $final_response->setProtocolVersion($response->getProtocolVersion());
+    $final_response->setCharset($response->getCharset());
     $final_response->headers->add($response->headers->all());
     if ($final_response instanceof CacheableResponseInterface) {
       $final_response->addCacheableDependency($response->getCacheableMetadata());
diff --git a/core/modules/rest/tests/src/Unit/EventSubscriber/ResourceResponseSubscriberTest.php b/core/modules/rest/tests/src/Unit/EventSubscriber/ResourceResponseSubscriberTest.php
index bb138fe..808f33d 100644
--- a/core/modules/rest/tests/src/Unit/EventSubscriber/ResourceResponseSubscriberTest.php
+++ b/core/modules/rest/tests/src/Unit/EventSubscriber/ResourceResponseSubscriberTest.php
@@ -9,7 +9,7 @@
 use Drupal\Core\Routing\RouteMatch;
 use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\rest\EventSubscriber\ResourceResponseSubscriber;
-use Drupal\rest\Plugin\ResourceBase;
+use Drupal\rest\ModifiedResourceResponse;
 use Drupal\rest\ResourceResponse;
 use Drupal\rest\ResourceResponseInterface;
 use Drupal\serialization\Encoder\JsonEncoder;
@@ -25,7 +25,7 @@
 
 /**
  * @coversDefaultClass \Drupal\rest\EventSubscriber\ResourceResponseSubscriber
- * @group restkak
+ * @group rest
  */
 class ResourceResponseSubscriberTest extends UnitTestCase {
 
@@ -113,7 +113,7 @@ public function testResponseFormat($methods, array $supported_formats, $request_
    *
    * @dataProvider providerTestResponseFormat
    */
-  public function testOnRespond($methods, array $supported_formats, $request_format, array $request_headers, $request_body, $expected_response_format, $expected_response_content_type, $expected_response_content) {
+  public function testOnRespondWithCacheableResponse($methods, array $supported_formats, $request_format, array $request_headers, $request_body, $expected_response_format, $expected_response_content_type, $expected_response_content) {
     $rest_config_name = $this->randomMachineName();
 
     $parameters = [];
@@ -132,14 +132,13 @@ public function testOnRespond($methods, array $supported_formats, $request_forma
       $route_requirement_key_format = $request->isMethodSafe() ? '_format' : '_content_type_format';
       $route_match = new RouteMatch('test', new Route('/rest/test', ['_rest_resource_config' => $rest_config_name], [$route_requirement_key_format => implode('|', $supported_formats)]));
 
-
       // The RequestHandler must return a ResourceResponseInterface object.
       $handler_response = new ResourceResponse($method !== 'DELETE' ? ['REST' => 'Drupal'] : NULL);
       $this->assertInstanceOf(ResourceResponseInterface::class, $handler_response);
       $this->assertInstanceOf(CacheableResponseInterface::class, $handler_response);
 
       // The ResourceResponseSubscriber must then generate a response body and
-      // transform it to a plain (Cacheable)Response object.
+      // transform it to a plain CacheableResponse object.
       $resource_response_subscriber = $this->getFunctioningResourceResponseSubscriber($route_match);
       $event = new FilterResponseEvent(
         $this->prophesize(HttpKernelInterface::class)->reveal(),
@@ -150,9 +149,59 @@ public function testOnRespond($methods, array $supported_formats, $request_forma
       $resource_response_subscriber->onRespond($event);
       $final_response = $event->getResponse();
       $this->assertNotInstanceOf(ResourceResponseInterface::class, $final_response);
-      $this->assertInstanceOf(CacheableResponseInterface::class, $handler_response);
-      $this->assertSame($expected_response_content_type, $handler_response->headers->get('Content-Type'));
-      $this->assertEquals($expected_response_content, $handler_response->getContent());
+      $this->assertInstanceOf(CacheableResponseInterface::class, $final_response);
+      $this->assertSame($expected_response_content_type, $final_response->headers->get('Content-Type'));
+      $this->assertEquals($expected_response_content, $final_response->getContent());
+    }
+  }
+
+  /**
+   * @covers ::onRespond
+   * @covers ::getResponseFormat
+   * @covers ::renderResponseBody
+   * @covers ::flattenResponse
+   *
+   * @dataProvider providerTestResponseFormat
+   */
+  public function testOnRespondWithUncacheableResponse($methods, array $supported_formats, $request_format, array $request_headers, $request_body, $expected_response_format, $expected_response_content_type, $expected_response_content) {
+    $rest_config_name = $this->randomMachineName();
+
+    $parameters = [];
+    if ($request_format !== FALSE) {
+      $parameters['_format'] = $request_format;
+    }
+
+    foreach ($request_headers as $key => $value) {
+      unset($request_headers[$key]);
+      $key = strtoupper(str_replace('-', '_', $key));
+      $request_headers[$key] = $value;
+    }
+
+    foreach ($methods as $method) {
+      $request = Request::create('/rest/test', $method, $parameters, [], [], $request_headers, $request_body);
+      $route_requirement_key_format = $request->isMethodSafe() ? '_format' : '_content_type_format';
+      $route_match = new RouteMatch('test', new Route('/rest/test', ['_rest_resource_config' => $rest_config_name], [$route_requirement_key_format => implode('|', $supported_formats)]));
+
+      // The RequestHandler must return a ResourceResponseInterface object.
+      $handler_response = new ModifiedResourceResponse($method !== 'DELETE' ? ['REST' => 'Drupal'] : NULL);
+      $this->assertInstanceOf(ResourceResponseInterface::class, $handler_response);
+      $this->assertNotInstanceOf(CacheableResponseInterface::class, $handler_response);
+
+      // The ResourceResponseSubscriber must then generate a response body and
+      // transform it to a plain Response object.
+      $resource_response_subscriber = $this->getFunctioningResourceResponseSubscriber($route_match);
+      $event = new FilterResponseEvent(
+        $this->prophesize(HttpKernelInterface::class)->reveal(),
+        $request,
+        HttpKernelInterface::MASTER_REQUEST,
+        $handler_response
+      );
+      $resource_response_subscriber->onRespond($event);
+      $final_response = $event->getResponse();
+      $this->assertNotInstanceOf(ResourceResponseInterface::class, $final_response);
+      $this->assertNotInstanceOf(CacheableResponseInterface::class, $final_response);
+      $this->assertSame($expected_response_content_type, $final_response->headers->get('Content-Type'));
+      $this->assertEquals($expected_response_content, $final_response->getContent());
     }
   }
 
@@ -320,15 +369,3 @@ public function providerTestResponseFormat() {
   }
 
 }
-
-/**
- * Stub class where we can prophesize methods.
- */
-class StubRequestHandlerResourcePlugin extends ResourceBase {
-
-  function get() {}
-  function post() {}
-  function patch() {}
-  function delete() {}
-
-}