diff --git a/core/lib/Drupal/Core/Lock/LockBackendInterface.php b/core/lib/Drupal/Core/Lock/LockBackendInterface.php
index 778e616..ca2a4d8 100644
--- a/core/lib/Drupal/Core/Lock/LockBackendInterface.php
+++ b/core/lib/Drupal/Core/Lock/LockBackendInterface.php
@@ -59,10 +59,14 @@
  * \Drupal::lock()->acquire() and \Drupal::lock()->wait() will automatically
  * break (delete) a lock whose duration has exceeded the timeout specified when
  * it was acquired.
+ *
+ * @} End of "defgroup lock".
  */
 
 /**
  * Lock backend interface.
+ *
+ * @ingroup lock
  */
 interface LockBackendInterface {
 
@@ -131,7 +135,3 @@ public function releaseAll($lockId = NULL);
    */
   public function getLockId();
 }
-
-/**
- * @} End of "defgroup lock".
- */
diff --git a/core/modules/system/lib/Drupal/system/Tests/Lock/LockFunctionalTest.php b/core/modules/system/lib/Drupal/system/Tests/Lock/LockFunctionalTest.php
index d72c667..d105c10 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Lock/LockFunctionalTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Lock/LockFunctionalTest.php
@@ -33,36 +33,37 @@ public static function getInfo() {
    * Confirms that we can acquire and release locks in two parallel requests.
    */
   public function testLockAcquire() {
+    $lock = $this->container->get('lock');
     $lock_acquired = 'TRUE: Lock successfully acquired in system_test_lock_acquire()';
     $lock_not_acquired = 'FALSE: Lock not acquired in system_test_lock_acquire()';
-    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock acquired by this request.', 'Lock');
-    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock extended by this request.', 'Lock');
-    \Drupal::lock()->release('system_test_lock_acquire');
+    $this->assertTrue($lock->acquire('system_test_lock_acquire'), 'Lock acquired by this request.', 'Lock');
+    $this->assertTrue($lock->acquire('system_test_lock_acquire'), 'Lock extended by this request.', 'Lock');
+    $lock->release('system_test_lock_acquire');
 
     // Cause another request to acquire the lock.
     $this->drupalGet('system-test/lock-acquire');
     $this->assertText($lock_acquired, 'Lock acquired by the other request.', 'Lock');
     // The other request has finished, thus it should have released its lock.
-    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock acquired by this request.', 'Lock');
+    $this->assertTrue($lock->acquire('system_test_lock_acquire'), 'Lock acquired by this request.', 'Lock');
     // This request holds the lock, so the other request cannot acquire it.
     $this->drupalGet('system-test/lock-acquire');
     $this->assertText($lock_not_acquired, 'Lock not acquired by the other request.', 'Lock');
-    \Drupal::lock()->release('system_test_lock_acquire');
+    $lock->release('system_test_lock_acquire');
 
     // Try a very short timeout and lock breaking.
-    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_acquire', 0.5), 'Lock acquired by this request.', 'Lock');
+    $this->assertTrue($lock->acquire('system_test_lock_acquire', 0.5), 'Lock acquired by this request.', 'Lock');
     sleep(1);
     // The other request should break our lock.
     $this->drupalGet('system-test/lock-acquire');
     $this->assertText($lock_acquired, 'Lock acquired by the other request, breaking our lock.', 'Lock');
     // We cannot renew it, since the other thread took it.
-    $this->assertFalse(\Drupal::lock()->acquire('system_test_lock_acquire'), 'Lock cannot be extended by this request.', 'Lock');
+    $this->assertFalse($lock->acquire('system_test_lock_acquire'), 'Lock cannot be extended by this request.', 'Lock');
 
     // Check the shut-down function.
     $lock_acquired_exit = 'TRUE: Lock successfully acquired in system_test_lock_exit()';
     $lock_not_acquired_exit = 'FALSE: Lock not acquired in system_test_lock_exit()';
     $this->drupalGet('system-test/lock-exit');
     $this->assertText($lock_acquired_exit, 'Lock acquired by the other request before exit.', 'Lock');
-    $this->assertTrue(\Drupal::lock()->acquire('system_test_lock_exit'), 'Lock acquired by this request after the other request exits.', 'Lock');
+    $this->assertTrue($lock->acquire('system_test_lock_exit'), 'Lock acquired by this request after the other request exits.', 'Lock');
   }
 }