diff --git a/core/core.services.yml b/core/core.services.yml
index 72a54ac..b68dd90 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -169,7 +169,8 @@ services:
     arguments: ['@request_stack', '@url_generator']
   form_cache:
     class: Drupal\Core\Form\FormCache
-    arguments: ['@keyvalue.expirable', '@module_handler', '@?csrf_token']
+    arguments: ['@keyvalue.expirable', '@module_handler', '@current_user', '@csrf_token']
+    public: false  # Private to form_builder
   keyvalue:
     class: Drupal\Core\KeyValueStore\KeyValueFactory
     arguments: ['@service_container', '%factory.keyvalue%']
diff --git a/core/includes/form.inc b/core/includes/form.inc
index 3fa3056..4938933 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -23,24 +23,24 @@
  * Fetches a form from the cache.
  *
  * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.
- *   Use \Drupal::service('form_cache')->getCache().
+ *   Use \Drupal::formBuilder()->getCache().
  *
  * @see \Drupal\Core\Form\FormCacheInterface::getCache().
  */
 function form_get_cache($form_build_id, FormStateInterface $form_state) {
-  return \Drupal::service('form_cache')->getCache($form_build_id, $form_state);
+  return \Drupal::formBuilder()->getCache($form_build_id, $form_state);
 }
 
 /**
  * Stores a form in the cache.
  *
  * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.
- *   Use \Drupal::service('form_cache')->setCache().
+ *   Use \Drupal::formBuilder()->setCache().
  *
  * @see \Drupal\Core\Form\FormCacheInterface::setCache().
  */
 function form_set_cache($form_build_id, $form, FormStateInterface $form_state) {
-  \Drupal::service('form_cache')->setCache($form_build_id, $form, $form_state);
+  \Drupal::formBuilder()->setCache($form_build_id, $form, $form_state);
 }
 
 /**
diff --git a/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
index 40d15e8..429aceb 100644
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -99,6 +99,8 @@ class FormBuilder implements FormBuilderInterface, FormValidatorInterface, FormS
   protected $formSubmitter;
 
   /**
+   * The form cache.
+   *
    * @var \Drupal\Core\Form\FormCacheInterface
    */
   protected $formCache;
diff --git a/core/lib/Drupal/Core/Form/FormCache.php b/core/lib/Drupal/Core/Form/FormCache.php
index adf9865..d627828 100644
--- a/core/lib/Drupal/Core/Form/FormCache.php
+++ b/core/lib/Drupal/Core/Form/FormCache.php
@@ -11,6 +11,7 @@
 use Drupal\Core\Access\CsrfTokenGenerator;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\KeyValueStore\KeyValueExpirableFactoryInterface;
+use Drupal\Core\Session\AccountInterface;
 
 /**
  * Encapsulates the caching of a form and its form state.
@@ -55,12 +56,15 @@ class FormCache implements FormCacheInterface {
    *   stores for the form cache and form state cache.
    * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
    *   The module handler.
+   * @param \Drupal\Core\Session\AccountInterface $current_user
+   *   The current user.
    * @param \Drupal\Core\Access\CsrfTokenGenerator $csrf_token
    *   The CSRF token generator.
    */
-  public function __construct(KeyValueExpirableFactoryInterface $key_value_expirable_factory, ModuleHandlerInterface $module_handler, CsrfTokenGenerator $csrf_token = NULL) {
+  public function __construct(KeyValueExpirableFactoryInterface $key_value_expirable_factory, ModuleHandlerInterface $module_handler, AccountInterface $current_user, CsrfTokenGenerator $csrf_token = NULL) {
     $this->keyValueExpirableFactory = $key_value_expirable_factory;
     $this->moduleHandler = $module_handler;
+    $this->currentUser = $current_user;
     $this->csrfToken = $csrf_token;
   }
 
@@ -69,7 +73,7 @@ public function __construct(KeyValueExpirableFactoryInterface $key_value_expirab
    */
   public function getCache($form_build_id, FormStateInterface $form_state) {
     if ($form = $this->keyValueExpirableFactory->get('form')->get($form_build_id)) {
-      if ((isset($form['#cache_token']) && $this->csrfToken->validate($form['#cache_token'])) || (!isset($form['#cache_token']) && $this->currentUser()->isAnonymous())) {
+      if ((isset($form['#cache_token']) && $this->csrfToken->validate($form['#cache_token'])) || (!isset($form['#cache_token']) && $this->currentUser->isAnonymous())) {
         $this->loadCachedFormState($form_build_id, $form_state);
         return $form;
       }
@@ -120,7 +124,7 @@ public function setCache($form_build_id, $form, FormStateInterface $form_state)
 
     // Cache form structure.
     if (isset($form)) {
-      if ($this->currentUser()->isAuthenticated()) {
+      if ($this->currentUser->isAuthenticated()) {
         $form['#cache_token'] = $this->csrfToken->get();
       }
       $this->keyValueExpirableFactory->get('form')->setWithExpire($form_build_id, $form, $expire);
@@ -137,16 +141,4 @@ public function setCache($form_build_id, $form, FormStateInterface $form_state)
     }
   }
 
-  /**
-   * Gets the current active user.
-   *
-   * @return \Drupal\Core\Session\AccountInterface
-   */
-  protected function currentUser() {
-    if (!$this->currentUser && \Drupal::hasService('current_user')) {
-      $this->currentUser = \Drupal::currentUser();
-    }
-    return $this->currentUser;
-  }
-
 }
diff --git a/core/tests/Drupal/Tests/Core/Form/FormCacheTest.php b/core/tests/Drupal/Tests/Core/Form/FormCacheTest.php
index c132ea6..a9f28c6 100644
--- a/core/tests/Drupal/Tests/Core/Form/FormCacheTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormCacheTest.php
@@ -93,8 +93,7 @@ protected function setUp() {
       ->disableOriginalConstructor()
       ->getMock();
     $this->account = $this->getMock('Drupal\Core\Session\AccountInterface');
-    $this->formCache = new TestFormCache($this->keyValueExpirableFactory, $this->moduleHandler, $this->csrfToken);
-    $this->formCache->setCurrentUser($this->account);
+    $this->formCache = new FormCache($this->keyValueExpirableFactory, $this->moduleHandler, $this->account, $this->csrfToken);
   }
 
   /**
@@ -401,14 +400,3 @@ public function testSetCacheWithSafeStrings() {
   }
 
 }
-
-class TestFormCache extends FormCache {
-
-  /**
-   * @param \Drupal\Core\Session\AccountInterface $account
-   */
-  public function setCurrentUser(AccountInterface $account) {
-    $this->currentUser = $account;
-  }
-
-}