diff --git a/core/modules/rest/lib/Drupal/rest/Plugin/views/display/RestExport.php b/core/modules/rest/lib/Drupal/rest/Plugin/views/display/RestExport.php
index bec2bd1..694a422 100644
--- a/core/modules/rest/lib/Drupal/rest/Plugin/views/display/RestExport.php
+++ b/core/modules/rest/lib/Drupal/rest/Plugin/views/display/RestExport.php
@@ -60,7 +60,7 @@ class RestExport extends PathPluginBase {
    *
    * @var string
    */
-  protected $contentType;
+  protected $contentType = 'json';
 
   /**
    * The mime type for the response.
@@ -79,7 +79,14 @@ public function initDisplay(ViewExecutable $view, array &$display, array &$optio
     $negotiation = $container->get('content_negotiation');
     $request = $container->get('request');
 
-    $this->setContentType($negotiation->getContentType($request));
+    $request_content_type = $negotiation->getContentType($request);
+    // Only use the requested content type if it's not 'html'. If it is then
+    // default to 'json' to aid debugging.
+    // @todo Remove the need for this when we have better content negotiation.
+    if ($request_content_type != 'html') {
+      $this->setContentType($request_content_type);
+    }
+
     $this->setMimeType($request->getMimeType($this->contentType));
   }
 
diff --git a/core/modules/rest/lib/Drupal/rest/Tests/Views/StyleSerializerTest.php b/core/modules/rest/lib/Drupal/rest/Tests/Views/StyleSerializerTest.php
index ecf81f6..ccec21c 100644
--- a/core/modules/rest/lib/Drupal/rest/Tests/Views/StyleSerializerTest.php
+++ b/core/modules/rest/lib/Drupal/rest/Tests/Views/StyleSerializerTest.php
@@ -151,6 +151,15 @@ public function testReponseFormatConfiguration() {
     $this->drupalPost(NULL, array(), t('Save'));
 
     // Should return a 200.
+    // @todo This should be fixed when we have better content negotiation.
+    $this->drupalGet('test/serialize/field', array(), array('Accept: */*'));
+    $this->assertResponse(200, 'A 200 response was returned when HTML was requested.');
+
+    // Should return a 200. Emulates a sample firefow header.
+    $this->drupalGet('test/serialize/field', array(), array('Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'));
+    $this->assertResponse(200, 'A 200 response was returned when HTML was requested.');
+
+    // Should return a 200.
     $this->drupalGet('test/serialize/field', array(), array('Accept: application/json'));
     $this->assertResponse(200, 'A 200 response was returned when JSON was requested.');
     // Should return a 200.