diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index cd4991d..c382463 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -910,17 +910,8 @@ protected function setUp() {
 
     $request = \Drupal::request();
     // If there is a session manager, close and save the session.
-    $session_manager_state = 0;
     if (\Drupal::getContainer()->initialized('session_manager')) {
-      $session_manager = \Drupal::service('session_manager');
-      if ($session_manager->isStartedLazy()) {
-        $session_manager_state |= 0x1;
-      }
-      if ($session_manager->isStarted()) {
-        $session_manager_state |= 0x2;
-      }
-      $session_manager->save();
-      unset($session_manager);
+      \Drupal::service('session_manager')->save();
     }
 
     $this->kernel = DrupalKernel::createFromRequest($request, drupal_classloader(), 'prod', TRUE);
@@ -929,13 +920,6 @@ protected function setUp() {
     // disk. This forces us to not accidently load the parent site.
     $container = $this->kernel->rebuildContainer();
 
-    if ($session_manager_state & 0x1) {
-      $container->get('session_manager')->startLazy();
-    }
-    if ($session_manager_state & 0x2) {
-      $container->get('session_manager')->start();
-    }
-
     $config = $container->get('config.factory');
 
     // Manually create and configure private and temporary files directories.