diff --git a/core/lib/Drupal/Core/Session/AccountProxy.php b/core/lib/Drupal/Core/Session/AccountProxy.php
index a50a289..ba4d880 100644
--- a/core/lib/Drupal/Core/Session/AccountProxy.php
+++ b/core/lib/Drupal/Core/Session/AccountProxy.php
@@ -23,9 +23,19 @@ class AccountProxy implements AccountProxyInterface {
   protected $account;
 
   /**
+   * Account id.
+   *
+   * @var int
+   */
+  protected $id = 0;
+
+  /**
    * Initial account id.
    *
    * @var int
+   *
+   * @deprecated in Drupal 8.1.9 and to be removed in Drupal 9.
+   *   Use $this->id instead.
    */
   protected $initialAccountId;
 
@@ -39,6 +49,7 @@ public function setAccount(AccountInterface $account) {
       $account = $account->getAccount();
     }
     $this->account = $account;
+    $this->id = $account->id();
     date_default_timezone_set(drupal_get_user_timezone());
   }
 
@@ -47,11 +58,11 @@ public function setAccount(AccountInterface $account) {
    */
   public function getAccount() {
     if (!isset($this->account)) {
-      if ($this->initialAccountId) {
+      if ($this->id) {
         // After the container is rebuilt, DrupalKernel sets the initial
         // account to the id of the logged in user. This is necessary in order
         // to refresh the user account reference here.
-        $this->setAccount($this->loadUserEntity($this->initialAccountId));
+        $this->setAccount($this->loadUserEntity($this->id));
       }
       else {
         $this->account = new AnonymousUserSession();
@@ -65,7 +76,7 @@ public function getAccount() {
    * {@inheritdoc}
    */
   public function id() {
-    return $this->getAccount()->id();
+    return $this->id;
   }
 
   /**
@@ -160,7 +171,7 @@ public function setInitialAccountId($account_id) {
       throw new \LogicException('AccountProxyInterface::setInitialAccountId() cannot be called after an account was set on the AccountProxy');
     }
 
-    $this->initialAccountId = $account_id;
+    $this->id = $this->initialAccountId = $account_id;
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/Core/Session/AccountProxyTest.php b/core/tests/Drupal/Tests/Core/Session/AccountProxyTest.php
new file mode 100644
index 0000000..b087810
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Session/AccountProxyTest.php
@@ -0,0 +1,53 @@
+<?php
+
+namespace Drupal\Tests\Core\Session;
+
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Tests\UnitTestCase;
+use Drupal\Core\Session\AccountProxy;
+
+/**
+ * @coversDefaultClass \Drupal\Core\Session\AccountProxy
+ * @group Session
+ */
+class AccountProxyTest extends UnitTestCase {
+
+  /**
+   * @covers ::id
+   * @covers ::setInitialAccountId
+   */
+  public function testId() {
+    $account_proxy = new AccountProxy();
+    $this->assertSame(0, $account_proxy->id());
+    $account_proxy->setInitialAccountId(1);
+    $this->assertFalse(\Drupal::hasContainer());
+    // If the following call loaded the user entity it would call
+    // AccountProxy::loadUserEntity() which would fail because the container
+    // does not exist.
+    $this->assertSame(1, $account_proxy->id());
+    $current_user = $this->prophesize(AccountInterface::class);
+    $current_user->id()->willReturn(2);
+    $account_proxy->setAccount($current_user->reveal());
+    $this->assertSame(2, $account_proxy->id());
+  }
+
+  /**
+   * @covers ::setInitialAccountId
+   */
+  public function testSetInitialAccountIdException() {
+    $this->setExpectedException(\LogicException::class);
+    $account_proxy = new AccountProxy();
+    $current_user = $this->prophesize(AccountInterface::class);
+    $account_proxy->setAccount($current_user->reveal());
+    $account_proxy->setInitialAccountId(1);
+  }
+
+}
+
+namespace Drupal\Core\Session ;
+
+if (!function_exists('drupal_get_user_timezone')) {
+  function drupal_get_user_timezone() {
+    return date_default_timezone_get();
+  }
+}