diff --git a/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php
index f4b4506..8f1cf3e 100644
--- a/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php
@@ -172,7 +172,7 @@ protected function onJson(GetResponseForExceptionEvent $event) {
 
     // Display the message if the current error reporting level allows this type
     // of message to be displayed,
-    $data = [];
+    $data = NULL;
     if (error_displayable($error) && $message = $exception->getMessage()) {
       $data = [sprintf('A fatal error occurred: %s', $message)];
     }
diff --git a/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
index 5f13978..7befb00 100644
--- a/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
@@ -39,7 +39,7 @@ protected static function getPriority() {
    *   The event to process.
    */
   public function on403(GetResponseForExceptionEvent $event) {
-    $response = new JsonResponse([], Response::HTTP_FORBIDDEN);
+    $response = new JsonResponse(NULL, Response::HTTP_FORBIDDEN);
     $event->setResponse($response);
   }
 
@@ -50,7 +50,7 @@ public function on403(GetResponseForExceptionEvent $event) {
    *   The event to process.
    */
   public function on404(GetResponseForExceptionEvent $event) {
-    $response = new JsonResponse([], Response::HTTP_NOT_FOUND);
+    $response = new JsonResponse(NULL, Response::HTTP_NOT_FOUND);
     $event->setResponse($response);
   }
 
@@ -61,7 +61,7 @@ public function on404(GetResponseForExceptionEvent $event) {
    *   The event to process.
    */
   public function on405(GetResponseForExceptionEvent $event) {
-    $response = new JsonResponse([], Response::HTTP_METHOD_NOT_ALLOWED);
+    $response = new JsonResponse(NULL, Response::HTTP_METHOD_NOT_ALLOWED);
     $event->setResponse($response);
   }
 
diff --git a/core/modules/editor/src/Tests/QuickEditIntegrationLoadingTest.php b/core/modules/editor/src/Tests/QuickEditIntegrationLoadingTest.php
index 5b62af1..cce6e04 100644
--- a/core/modules/editor/src/Tests/QuickEditIntegrationLoadingTest.php
+++ b/core/modules/editor/src/Tests/QuickEditIntegrationLoadingTest.php
@@ -90,7 +90,7 @@ public function testUsersWithoutPermission() {
       // Retrieving the untransformed text should result in an empty 403 response.
       $response = $this->drupalPost('editor/' . 'node/1/body/en/full', 'application/vnd.drupal-ajax', array());
       $this->assertResponse(403);
-      $this->assertIdentical('[]', $response);
+      $this->assertIdentical('{}', $response);
     }
   }
 
diff --git a/core/modules/quickedit/src/Tests/QuickEditLoadingTest.php b/core/modules/quickedit/src/Tests/QuickEditLoadingTest.php
index afdb728..a20663d 100644
--- a/core/modules/quickedit/src/Tests/QuickEditLoadingTest.php
+++ b/core/modules/quickedit/src/Tests/QuickEditLoadingTest.php
@@ -84,7 +84,7 @@ public function testUserWithoutPermission() {
     // Retrieving the metadata should result in an empty 403 response.
     $post = array('fields[0]' => 'node/1/body/en/full');
     $response = $this->drupalPost('quickedit/metadata', 'application/json', $post);
-    $this->assertIdentical('[]', $response);
+    $this->assertIdentical('{}', $response);
     $this->assertResponse(403);
 
     // Quick Edit's JavaScript would SearchRankingTestnever hit these endpoints if the metadata
@@ -92,11 +92,11 @@ public function testUserWithoutPermission() {
     // able to use any of the other endpoints either.
     $post = array('editors[0]' => 'form') + $this->getAjaxPageStatePostData();
     $response = $this->drupalPost('quickedit/attachments', 'application/vnd.drupal-ajax', $post);
-    $this->assertIdentical('[]', $response);
+    $this->assertIdentical('{}', $response);
     $this->assertResponse(403);
     $post = array('nocssjs' => 'true') + $this->getAjaxPageStatePostData();
     $response = $this->drupalPost('quickedit/form/' . 'node/1/body/en/full', 'application/vnd.drupal-ajax', $post);
-    $this->assertIdentical('[]', $response);
+    $this->assertIdentical('{}', $response);
     $this->assertResponse(403);
     $edit = array();
     $edit['form_id'] = 'quickedit_field_form';
@@ -107,11 +107,11 @@ public function testUserWithoutPermission() {
     $edit['body[0][format]'] = 'filtered_html';
     $edit['op'] = t('Save');
     $response = $this->drupalPost('quickedit/form/' . 'node/1/body/en/full', 'application/vnd.drupal-ajax', $edit);
-    $this->assertIdentical('[]', $response);
+    $this->assertIdentical('{}', $response);
     $this->assertResponse(403);
     $post = array('nocssjs' => 'true');
     $response = $this->drupalPost('quickedit/entity/' . 'node/1', 'application/json', $post);
-    $this->assertIdentical('[]', $response);
+    $this->assertIdentical('{}', $response);
     $this->assertResponse(403);
   }
 
diff --git a/core/modules/rest/src/Tests/ReadTest.php b/core/modules/rest/src/Tests/ReadTest.php
index dda6bc8..c730b89 100644
--- a/core/modules/rest/src/Tests/ReadTest.php
+++ b/core/modules/rest/src/Tests/ReadTest.php
@@ -60,7 +60,7 @@ public function testRead() {
       // Try to read an entity that does not exist.
       $response = $this->httpRequest($entity_type . '/9999', 'GET', NULL, $this->defaultMimeType);
       $this->assertResponse(404);
-      $this->assertText('A fatal error occurred: The "' . $entity_type . '" parameter was not converted for the path', 'Response message is correct.');
+      $this->assertText(Json::encode(['A fatal error occurred: The "' . $entity_type . '" parameter was not converted for the path']), 'Response message is correct.');
 
       // Make sure that field level access works and that the according field is
       // not available in the response. Only applies to entity_test.
@@ -79,14 +79,14 @@ public function testRead() {
       $this->drupalLogout();
       $response = $this->httpRequest($entity->getSystemPath(), 'GET', NULL, $this->defaultMimeType);
       $this->assertResponse(403);
-      $this->assertNull(Json::decode($response), 'No valid JSON found.');
+      $this->assertIdentical('{}', $response);
     }
     // Try to read a resource which is not REST API enabled.
     $account = $this->drupalCreateUser();
     $this->drupalLogin($account);
     $response = $this->httpRequest($account->getSystemPath(), 'GET', NULL, $this->defaultMimeType);
     $this->assertResponse(404);
-    $this->assertNull(Json::decode($response), 'No valid JSON found.');
+    $this->assertIdentical('{}', $response);
   }
 
   /**