diff --git a/core/lib/Drupal/Core/Form/FormSubmitter.php b/core/lib/Drupal/Core/Form/FormSubmitter.php
index 2602bc7316e10826d3e6d3de21fea1cf510f704e..78aca72665f549a5843051e1c2f450a5d9e095d2 100644
--- a/core/lib/Drupal/Core/Form/FormSubmitter.php
+++ b/core/lib/Drupal/Core/Form/FormSubmitter.php
@@ -169,7 +169,10 @@ public function redirectForm($form_state) {
       }
 
       $form_state['redirect_route']->setAbsolute();
-      return new RedirectResponse($form_state['redirect_route']->toString());
+      // According to RFC 7231, 303 See Other status code must be used
+      // to redirect user agent (and not default 302 Found).
+      // @see http://tools.ietf.org/html/rfc7231#section-6.4.4
+      return new RedirectResponse($form_state['redirect_route']->toString(), Response::HTTP_SEE_OTHER);
     }
 
     // Only invoke a redirection if redirect value was not set to FALSE.
@@ -188,7 +191,7 @@ public function redirectForm($form_state) {
             $status_code = $form_state['redirect'][2];
           }
           else {
-            $status_code = 302;
+            $status_code = Response::HTTP_SEE_OTHER;
           }
           return new RedirectResponse($this->urlGenerator->generateFromPath($form_state['redirect'][0], $options), $status_code);
         }
@@ -200,7 +203,7 @@ public function redirectForm($form_state) {
             install_goto($form_state['redirect']);
           }
           else {
-            return new RedirectResponse($this->urlGenerator->generateFromPath($form_state['redirect'], array('absolute' => TRUE)));
+            return new RedirectResponse($this->urlGenerator->generateFromPath($form_state['redirect'], array('absolute' => TRUE)), Response::HTTP_SEE_OTHER);
           }
         }
       }
@@ -211,7 +214,7 @@ public function redirectForm($form_state) {
         'query' => $request->query->all(),
         'absolute' => TRUE,
       ));
-      return new RedirectResponse($url);
+      return new RedirectResponse($url, Response::HTTP_SEE_OTHER);
     }
   }
 
diff --git a/core/modules/simpletest/src/Tests/SimpleTestTest.php b/core/modules/simpletest/src/Tests/SimpleTestTest.php
old mode 100755
new mode 100644
index b2fffb36d6027926927aaa196b59d6a7e693d996..9d16df38b155612870f5ca338bb8f7480dc9de22
--- a/core/modules/simpletest/src/Tests/SimpleTestTest.php
+++ b/core/modules/simpletest/src/Tests/SimpleTestTest.php
@@ -108,7 +108,7 @@ function testInternalBrowser() {
       $this->assertNotEqual($old_user_id, $this->container->get('current_user')->id(), 'Current user service updated.');
       $headers = $this->drupalGetHeaders(TRUE);
       $this->assertEqual(count($headers), 2, 'There was one intermediate request.');
-      $this->assertTrue(strpos($headers[0][':status'], '302') !== FALSE, 'Intermediate response code was 302.');
+      $this->assertTrue(strpos($headers[0][':status'], '303') !== FALSE, 'Intermediate response code was 303.');
       $this->assertFalse(empty($headers[0]['location']), 'Intermediate request contained a Location header.');
       $this->assertEqual($this->getUrl(), $headers[0]['location'], 'HTTP redirect was followed');
       $this->assertFalse($this->drupalGetHeader('Location'), 'Headers from intermediate request were reset.');
diff --git a/core/tests/Drupal/Tests/Core/Form/FormSubmitterTest.php b/core/tests/Drupal/Tests/Core/Form/FormSubmitterTest.php
index 5dcc66816b604b26b6310c67c74d2dd4c011af9a..1d65e50f33e90dc71543b61a43cd3ee3a647c3e2 100644
--- a/core/tests/Drupal/Tests/Core/Form/FormSubmitterTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormSubmitterTest.php
@@ -116,7 +116,7 @@ public function providerTestHandleFormSubmissionWithResponses() {
    *
    * @dataProvider providerTestRedirectWithResult
    */
-  public function testRedirectWithResult($form_state, $result, $status = 302) {
+  public function testRedirectWithResult($form_state, $result, $status = 303) {
     $form_submitter = $this->getFormSubmitter();
     $this->urlGenerator->expects($this->once())
       ->method('generateFromPath')
@@ -141,7 +141,7 @@ public function testRedirectWithResult($form_state, $result, $status = 302) {
    *
    * @dataProvider providerTestRedirectWithRouteWithResult
    */
-  public function testRedirectWithRouteWithResult($form_state, $result, $status = 302) {
+  public function testRedirectWithRouteWithResult($form_state, $result, $status = 303) {
     $container = new ContainerBuilder();
     $container->set('url_generator', $this->urlGenerator);
     \Drupal::setContainer($container);