diff -u b/core/tests/Drupal/KernelTests/Core/Form/FormCacheTest.php b/core/tests/Drupal/KernelTests/Core/Form/FormCacheTest.php
--- b/core/tests/Drupal/KernelTests/Core/Form/FormCacheTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Form/FormCacheTest.php
@@ -106,8 +106,6 @@
    * Tests the form cache with an overridden cache expiration.
    */
   public function testCacheCustomExpiration() {
-    \Drupal::currentUser()->setAccount(new UserSession(['uid' => 1]));
-
     // Override form cache expiration so that the cached form expired yesterday.
     new Settings(['form_cache_expiration' => -1 * (24*60*60), 'hash_salt' => $this->randomMachineName()]);
     \Drupal::formBuilder()->setCache($this->formBuildId, $this->form, $this->formState);