diff --git a/core/lib/Drupal/Core/ContentNegotiation.php b/core/lib/Drupal/Core/ContentNegotiation.php
index 6302db8..b6ae0d1 100644
--- a/core/lib/Drupal/Core/ContentNegotiation.php
+++ b/core/lib/Drupal/Core/ContentNegotiation.php
@@ -41,6 +41,11 @@ public function getContentType(Request $request) {
       return 'ajax';
     }
 
+    // Return HTML without looking at the weight.
+    if (strpos($request->headers->get('Accept'), 'text/html') !== FALSE) {
+      return 'html';
+    }
+
     foreach ($request->getAcceptableContentTypes() as $mime_type) {
       $format = $request->getFormat($mime_type);
       if (!is_null($format)) {
diff --git a/core/modules/system/lib/Drupal/system/Tests/DrupalKernel/ContentNegotiationTest.php b/core/modules/system/lib/Drupal/system/Tests/DrupalKernel/ContentNegotiationTest.php
new file mode 100644
index 0000000..f13c16c
--- /dev/null
+++ b/core/modules/system/lib/Drupal/system/Tests/DrupalKernel/ContentNegotiationTest.php
@@ -0,0 +1,56 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\system\Tests\DrupalKernel\ContentNegotiationTest.
+ */
+
+namespace Drupal\system\Tests\DrupalKernel;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Tests content negotation.
+ */
+class ContentNegotiationTest extends WebTestBase {
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Content negotiation',
+      'description' => 'Tests content negotiation.',
+      'group' => 'DrupalKernel',
+    );
+  }
+
+  /**
+   * Verifies HTML responses for bogus Accept headers.
+   *
+   * Drupal does not fully support older browsers, but a page output is still
+   * expected.
+   *
+   * @see http://drupal.org/node/1716790
+   */
+  function testBogusAcceptHeader() {
+    $tests = array(
+      // @see https://bugs.webkit.org/show_bug.cgi?id=27267
+      'Firefox 3.5 (2009)' => 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
+      'IE8 (2009)' => 'image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-silverlight, */*',
+      'Opera (2009)' => 'text/html, application/xml;q=0.9, application/xhtml+xml, image/png, image/jpeg, image/gif, image/x-xbitmap, */*;q=0.1',
+      'Chrome (2009)' => 'application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5',
+      // @see https://github.com/symfony/symfony/pull/564
+      'Firefox 3.6 (2010)' => 'text/html,application/xhtml+xml,application/json,application/xml;q=0.9,*/*;q=0.8',
+      'Safari (2010)' => '*/*',
+      'Opera (2010)' => 'image/jpeg,image/gif,image/x-xbitmap,text/html,image/webp,image/png,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.1',
+      // @see http://drupal.org/node/1716790
+      'Safari (2010), iOS 4.2.1 (2012)' => 'application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5',
+      'Android #1 (2012)' => 'application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5',
+      'Android #2 (2012)' => 'text/xml,text/html,application/xhtml+xml,image/png,text/plain,*/*;q=0.8',
+    );
+    foreach ($tests as $case => $header) {
+      $this->drupalGet('', array(), array('Accept: ' . $header));
+      $this->assertNoText('Unsupported Media Type', '"Unsupported Media Type" not found for ' . $case);
+      $this->assertText(t('Log in'), '"Log in" found for ' . $case);
+    }
+  }
+
+}