diff --git a/core/lib/Drupal/Core/Controller/ExceptionController.php b/core/lib/Drupal/Core/Controller/ExceptionController.php
index 66a6215..04a8a3f 100644
--- a/core/lib/Drupal/Core/Controller/ExceptionController.php
+++ b/core/lib/Drupal/Core/Controller/ExceptionController.php
@@ -12,7 +12,7 @@
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpKernel\HttpKernelInterface;
-use Symfony\Component\HttpKernel\Exception\FlattenException;
+use Symfony\Component\Debug\Exception\FlattenException;
 
 use Drupal\Core\ContentNegotiation;
 
@@ -42,7 +42,7 @@ public function __construct(ContentNegotiation $negotiation) {
   /**
    * Handles an exception on a request.
    *
-   * @param \Symfony\Component\HttpKernel\Exception\FlattenException $exception
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
    *   The flattened exception.
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request that generated the exception.
@@ -63,10 +63,13 @@ public function execute(FlattenException $exception, Request $request) {
   /**
    * Processes a MethodNotAllowed exception into an HTTP 405 response.
    *
-   * @param Symfony\Component\HttpKernel\Exception\FlattenException $exception
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
    *   The flattened exception.
-   * @param Symfony\Component\HttpFoundation\Request $request
+   * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request object that triggered this exception.
+   *
+   * @return \Symfony\Component\HttpFoundation\Response
+   *   A response object to be sent to the server.
    */
   public function on405Html(FlattenException $exception, Request $request) {
     return new Response('Method Not Allowed', 405);
@@ -75,10 +78,13 @@ public function on405Html(FlattenException $exception, Request $request) {
   /**
    * Processes an AccessDenied exception into an HTTP 403 response.
    *
-   * @param Symfony\Component\HttpKernel\Exception\FlattenException $exception
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
    *   The flattened exception.
-   * @param Symfony\Component\HttpFoundation\Request $request
+   * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request object that triggered this exception.
+   *
+   * @return \Symfony\Component\HttpFoundation\Response
+   *   A response object to be sent to the server.
    */
   public function on403Html(FlattenException $exception, Request $request) {
     $system_path = $request->attributes->get('_system_path');
@@ -130,10 +136,13 @@ public function on403Html(FlattenException $exception, Request $request) {
   /**
    * Processes a NotFound exception into an HTTP 404 response.
    *
-   * @param Symfony\Component\HttpKernel\Exception\FlattenException $exception
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
    *   The flattened exception.
-   * @param Sonfony\Component\HttpFoundation\Request $request
+   * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request object that triggered this exception.
+   *
+   * @return \Symfony\Component\HttpFoundation\Response
+   *   A response object to be sent to the server.
    */
   public function on404Html(FlattenException $exception, Request $request) {
     watchdog('page not found', check_plain($request->attributes->get('_system_path')), NULL, WATCHDOG_WARNING);
@@ -202,10 +211,13 @@ public function on404Html(FlattenException $exception, Request $request) {
   /**
    * Processes a generic exception into an HTTP 500 response.
    *
-   * @param Symfony\Component\HttpKernel\Exception\FlattenException $exception
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
    *   Metadata about the exception that was thrown.
-   * @param Symfony\Component\HttpFoundation\Request $request
+   * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request object that triggered this exception.
+   *
+   * @return \Symfony\Component\HttpFoundation\Response
+   *   A response object to be sent to the server.
    */
   public function on500Html(FlattenException $exception, Request $request) {
     $error = $this->decodeException($exception);
@@ -270,10 +282,13 @@ public function on500Html(FlattenException $exception, Request $request) {
   /**
    * Processes an AccessDenied exception that occured on a JSON request.
    *
-   * @param Symfony\Component\HttpKernel\Exception\FlattenException $exception
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
    *   The flattened exception.
-   * @param Symfony\Component\HttpFoundation\Request $request
+   * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request object that triggered this exception.
+   *
+   * @return \Symfony\Component\HttpFoundation\JsonResponse
+   *   A JSON response object to be sent to the server.
    */
   public function on403Json(FlattenException $exception, Request $request) {
     $response = new JsonResponse();
@@ -284,10 +299,13 @@ public function on403Json(FlattenException $exception, Request $request) {
   /**
    * Processes a NotFound exception that occured on a JSON request.
    *
-   * @param Symfony\Component\HttpKernel\Exception\FlattenException $exception
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
    *   The flattened exception.
-   * @param Symfony\Component\HttpFoundation\Request $request
+   * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request object that triggered this exception.
+   *
+   * @return \Symfony\Component\HttpFoundation\JsonResponse
+   *   A JSON response object to be sent to the server.
    */
   public function on404Json(FlattenException $exception, Request $request) {
     $response = new JsonResponse();
@@ -298,10 +316,13 @@ public function on404Json(FlattenException $exception, Request $request) {
   /**
    * Processes a MethodNotAllowed exception that occured on a JSON request.
    *
-   * @param Symfony\Component\HttpKernel\Exception\FlattenException $exception
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
    *   The flattened exception.
-   * @param Symfony\Component\HttpFoundation\Request $request
+   * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request object that triggered this exception.
+   *
+   * @return \Symfony\Component\HttpFoundation\JsonResponse
+   *   A JSON response object to be sent to the server.
    */
   public function on405Json(FlattenException $exception, Request $request) {
     $response = new JsonResponse();
@@ -316,7 +337,11 @@ public function on405Json(FlattenException $exception, Request $request) {
    * @todo This should get refactored. FlattenException could use some
    *   improvement as well.
    *
+   * @param \Symfony\Component\Debug\Exception\FlattenException $exception
+   *  The flattened exception.
+   *
    * @return array
+   *   The exception that was contained within the FlattenException .
    */
   protected function decodeException(FlattenException $exception) {
     $message = $exception->getMessage();
@@ -371,7 +396,7 @@ protected function decodeException(FlattenException $exception) {
    * @param $backtrace
    *   A standard PHP backtrace.
    *
-   * @return
+   * @return array
    *   An associative array with keys 'file', 'line' and 'function'.
    */
   protected function getLastCaller($backtrace) {
diff --git a/core/tests/Drupal/Tests/Core/Controller/ExceptionControllerTest.php b/core/tests/Drupal/Tests/Core/Controller/ExceptionControllerTest.php
index 020daab..88a010d 100644
--- a/core/tests/Drupal/Tests/Core/Controller/ExceptionControllerTest.php
+++ b/core/tests/Drupal/Tests/Core/Controller/ExceptionControllerTest.php
@@ -11,7 +11,7 @@
 use Drupal\Core\Controller\ExceptionController;
 use Drupal\Tests\UnitTestCase;
 use Symfony\Component\HttpFoundation\Request;
-use Symfony\Component\HttpKernel\Exception\FlattenException;
+use Symfony\Component\Debug\Exception\FlattenException;
 
 /**
  * Tests exception controller.