diff --git a/core/core.services.yml b/core/core.services.yml
index fac198c..56f1467 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -566,8 +566,12 @@ services:
     class: Symfony\Component\HttpKernel\HttpKernel
     arguments: ['@event_dispatcher', '@controller_resolver', '@request_stack']
   http_negotiation.format_negotiator:
-    class: Drupal\Core\FormatMapping
+    class: Drupal\Core\ContentNegotiation
     private: true
+  http_negotiation.wrapper_format_subscriber:
+    class: Drupal\Core\EventSubscriber\WrapperFormatSubscriber
+    tags:
+      - { name: event_subscriber }
   http_middleware.negotiation:
     class: Drupal\Core\StackMiddleware\NegotiationMiddleware
     arguments: ['@http_negotiation.format_negotiator']
diff --git a/core/lib/Drupal/Core/FormatMapping.php b/core/lib/Drupal/Core/ContentNegotiation.php
similarity index 89%
rename from core/lib/Drupal/Core/FormatMapping.php
rename to core/lib/Drupal/Core/ContentNegotiation.php
index 40e6aea..3322af8 100644
--- a/core/lib/Drupal/Core/FormatMapping.php
+++ b/core/lib/Drupal/Core/ContentNegotiation.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\Core\FormatMapping.
+ * Definition of Drupal\Core\ContentNegotiation.
  */
 
 namespace Drupal\Core;
@@ -15,7 +15,7 @@
  * @todo Replace this class with a real content negotiation library based on
  *   mod_negotiation. Development of that is a work in progress.
  */
-class FormatMapping {
+class ContentNegotiation {
 
   /**
    * Gets the normalized type of a request.
@@ -36,15 +36,12 @@ public function getContentType(Request $request) {
       return 'iframeupload';
     }
 
-    if ($type = $request->query->get('dialogType')) {
-      return 'drupal_' . $type;
-    }
-
     // Check all formats, if priority format is found return it.
     $first_found_format = FALSE;
+    $priority = array('html');
     foreach ($request->getAcceptableContentTypes() as $mime_type) {
       $format = $request->getFormat($mime_type);
-      if ($format === 'html') {
+      if (in_array($format, $priority, TRUE)) {
         return $format;
       }
       if (!is_null($format) && !$first_found_format) {
diff --git a/core/lib/Drupal/Core/EventSubscriber/WrapperFormatSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/WrapperFormatSubscriber.php
new file mode 100644
index 0000000..f293c57
--- /dev/null
+++ b/core/lib/Drupal/Core/EventSubscriber/WrapperFormatSubscriber.php
@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\EventSubscriber\WrapperFormatSubscriber.
+ */
+
+namespace Drupal\Core\EventSubscriber;
+
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+use Symfony\Component\HttpKernel\Event\GetResponseEvent;
+use Symfony\Component\HttpKernel\KernelEvents;
+
+/**
+ * Sets the wrapper format, if specified for the request.
+ */
+class WrapperFormatSubscriber implements EventSubscriberInterface {
+
+  const WRAPPER_FORMAT = '_wrapper_format';
+
+  /**
+   * Sets the wrapper format, if specified for the request.
+   */
+  public function onRequest(GetResponseEvent $event) {
+    $request = $event->getRequest();
+    if ($request->query->has(static::WRAPPER_FORMAT)) {
+      $request->setRequestFormat($request->query->get(static::WRAPPER_FORMAT));
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents() {
+    $events[KernelEvents::REQUEST][] = ['onRequest', 48];
+
+    return $events;
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Render/Element/RenderElement.php b/core/lib/Drupal/Core/Render/Element/RenderElement.php
index 87b9f02..7600f62 100644
--- a/core/lib/Drupal/Core/Render/Element/RenderElement.php
+++ b/core/lib/Drupal/Core/Render/Element/RenderElement.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Core\Render\Element;
 
+use Drupal\Core\EventSubscriber\WrapperFormatSubscriber;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\PluginBase;
 use Drupal\Core\Render\Element;
@@ -240,7 +241,7 @@ public static function preRenderAjaxForm($element) {
       $settings += array(
         'url' => isset($settings['callback']) ? Url::fromRoute('system.ajax') : NULL,
         'options' => array(),
-        'dialogType' => 'ajax',
+        WrapperFormatSubscriber::WRAPPER_FORMAT => 'ajax',
       );
 
       // @todo Legacy support. Remove in Drupal 8.
diff --git a/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php b/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php
index 8fa0173..295857d 100644
--- a/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php
+++ b/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\Core\StackMiddleware;
 
-use Drupal\Core\FormatMapping;
+use Drupal\Core\ContentNegotiation;
 use Drupal\Core\ContentNegotiationInterface;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpKernel\HttpKernelInterface;
@@ -29,7 +29,7 @@ class NegotiationMiddleware implements HttpKernelInterface {
   /**
    * The content negotiator.
    *
-   * @var \Drupal\Core\FormatMapping
+   * @var \Drupal\Core\ContentNegotiation
    */
   protected $negotiator;
 
@@ -45,10 +45,10 @@ class NegotiationMiddleware implements HttpKernelInterface {
    *
    * @param \Symfony\Component\HttpKernel\HttpKernelInterface $app
    *   The wrapper HTTP kernel
-   * @param \Drupal\Core\FormatMapping $negotiator
+   * @param \Drupal\Core\ContentNegotiation $negotiator
    *   The content negotiator.
    */
-  public function __construct(HttpKernelInterface $app, FormatMapping $negotiator) {
+  public function __construct(HttpKernelInterface $app, ContentNegotiation $negotiator) {
     $this->app = $app;
     $this->negotiator = $negotiator;
   }
diff --git a/core/misc/ajax.js b/core/misc/ajax.js
index 212a79f..b2eb6fb 100644
--- a/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -272,7 +272,7 @@
       else {
         ajax.options.url += '&';
       }
-      ajax.options.url += 'dialogType=' + element_settings.dialogType;
+      ajax.options.url += '_wrapper_format=' + element_settings.dialogType;
     }
 
     // Bind the ajaxSubmit function to the element event.
diff --git a/core/modules/ckeditor/js/ckeditor.js b/core/modules/ckeditor/js/ckeditor.js
index 5d9e969..7f9dbf0 100644
--- a/core/modules/ckeditor/js/ckeditor.js
+++ b/core/modules/ckeditor/js/ckeditor.js
@@ -161,7 +161,7 @@
       var $content = $('<div class="ckeditor-dialog-loading"><span style="top: -40px;" class="ckeditor-dialog-loading-link"><a>' + Drupal.t('Loading...') + '</a></span></div>');
       $content.appendTo($target);
       new Drupal.ajax('ckeditor-dialog', $content.find('a').get(0), {
-        dialogType: 'modal',
+        _wrapper_format: 'modal',
         dialog: dialogSettings,
         selector: '.ckeditor-dialog-loading-link',
         url: url,
diff --git a/core/modules/system/src/Tests/Ajax/DialogTest.php b/core/modules/system/src/Tests/Ajax/DialogTest.php
index 28a3d0c..741ee5d 100644
--- a/core/modules/system/src/Tests/Ajax/DialogTest.php
+++ b/core/modules/system/src/Tests/Ajax/DialogTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\system\Tests\Ajax;
 
+use Drupal\Core\EventSubscriber\WrapperFormatSubscriber;
 use Drupal\Core\Url;
 
 /**
@@ -165,7 +166,7 @@ public function testDialog() {
         'callback' => '::preview',
         'event' => 'click',
         'url' => Url::fromRoute('system.ajax')->toString(),
-        'dialogType' => 'ajax',
+        WrapperFormatSubscriber::WRAPPER_FORMAT => 'ajax',
         'submit' => [
           '_triggering_element_name' => 'op',
           '_triggering_element_value' => 'Preview',
diff --git a/core/tests/Drupal/Tests/Core/FormatMappingTest.php b/core/tests/Drupal/Tests/Core/ContentNegotationTest.php
similarity index 65%
rename from core/tests/Drupal/Tests/Core/FormatMappingTest.php
rename to core/tests/Drupal/Tests/Core/ContentNegotationTest.php
index f24e09b..d5f3081 100644
--- a/core/tests/Drupal/Tests/Core/FormatMappingTest.php
+++ b/core/tests/Drupal/Tests/Core/ContentNegotationTest.php
@@ -7,20 +7,20 @@
 
 namespace Drupal\Tests\Core;
 
-use Drupal\Core\FormatMapping;
+use Drupal\Core\ContentNegotiation;
 use Drupal\Tests\UnitTestCase;
 use Symfony\Component\HttpFoundation\Request;
 
 /**
- * @coversDefaultClass \Drupal\Core\FormatMapping
- * @group FormatMapping
+ * @coversDefaultClass \Drupal\Core\ContentNegotiation
+ * @group ContentNegotiation
  */
-class FormatMappingTest extends UnitTestCase {
+class ContentNegotiationTest extends UnitTestCase {
 
   /**
-   * @var \Drupal\Core\FormatMapping
+   * @var \Drupal\Core\ContentNegotiation
    */
-  protected $formatMapping;
+  protected $contentNegotiation;
 
   /**
    * {@inheritdoc}
@@ -28,7 +28,7 @@ class FormatMappingTest extends UnitTestCase {
   protected function setUp() {
     parent::setUp();
 
-    $this->formatMapping = new FormatMapping;
+    $this->contentNegotiation = new ContentNegotiation;
   }
 
   /**
@@ -40,7 +40,7 @@ public function testAjaxIframeUpload() {
     $request = new Request();
     $request->attributes->set('ajax_iframe_upload', '1');
 
-    $this->assertSame('iframeupload', $this->formatMapping->getContentType($request));
+    $this->assertSame('iframeupload', $this->contentNegotiation->getContentType($request));
   }
 
   /**
@@ -51,21 +51,16 @@ public function testAjaxIframeUpload() {
    */
   public function testAPriorityFormatIsFound($priority, $format) {
     $request = new Request();
+    $request->setFormat($format['format'], $format['mime_type']);
+    $request->headers->set('Accept', sprintf('%s,application/json', $format['mime_type']));
 
-    if ($format) {
-      $request->query->set('dialogType', $format);
-    }
-
-    $this->assertSame($priority, $this->formatMapping->getContentType($request));
+    $this->assertSame($priority, $this->contentNegotiation->getContentType($request));
   }
 
   public function priorityFormatProvider()
   {
     return [
-      ['drupal_dialog', 'dialog'],
-      ['drupal_modal', 'modal'],
-      ['drupal_ajax', 'ajax'],
-      ['html', ''],
+      ['html', ['format' => 'html', 'mime_type' => 'text/html']],
     ];
   }
 
@@ -78,7 +73,7 @@ public function testNoPriorityFormatIsFoundButReturnsTheFirstValidOne() {
     $request = new Request();
     $request->headers->set('Accept', 'application/rdf+xml');
 
-    $this->assertSame('rdf', $this->formatMapping->getContentType($request));
+    $this->assertSame('rdf', $this->contentNegotiation->getContentType($request));
   }
 
   /**
@@ -89,7 +84,7 @@ public function testNoPriorityFormatIsFoundButReturnsTheFirstValidOne() {
   public function testUnknowContentTypeReturnsHtmlByDefault() {
     $request = new Request();
 
-    $this->assertSame('html', $this->formatMapping->getContentType($request));
+    $this->assertSame('html', $this->contentNegotiation->getContentType($request));
   }
 
   /**
@@ -101,7 +96,7 @@ public function testUnknowContentTypeButAjaxRequest() {
     $request = new Request();
     $request->headers->set('X-Requested-With', 'XMLHttpRequest');
 
-    $this->assertSame('ajax', $this->formatMapping->getContentType($request));
+    $this->assertSame('ajax', $this->contentNegotiation->getContentType($request));
   }
 
 }