diff --git a/core/lib/Drupal/Core/Extension/Exception/UninstalledExtensionException.php b/core/lib/Drupal/Core/Extension/Exception/UninstalledExtensionException.php
index 8cfb9bf..5588a12 100644
--- a/core/lib/Drupal/Core/Extension/Exception/UninstalledExtensionException.php
+++ b/core/lib/Drupal/Core/Extension/Exception/UninstalledExtensionException.php
@@ -5,4 +5,4 @@
 /**
  * Exception class thrown when a specified extension has not been installed.
  */
-class UninstalledExtensionException extends \RuntimeException { }
+class UninstalledExtensionException extends \RuntimeException {}
diff --git a/core/lib/Drupal/Core/Extension/Exception/UnknownExtensionException.php b/core/lib/Drupal/Core/Extension/Exception/UnknownExtensionException.php
index 7daa4d1..b049cc6 100644
--- a/core/lib/Drupal/Core/Extension/Exception/UnknownExtensionException.php
+++ b/core/lib/Drupal/Core/Extension/Exception/UnknownExtensionException.php
@@ -5,4 +5,4 @@
 /**
  * Exception class thrown when a specified extension is not on the filesystem.
  */
-class UnknownExtensionException extends \RuntimeException { }
+class UnknownExtensionException extends \RuntimeException {}
diff --git a/core/lib/Drupal/Core/Extension/ThemeInstaller.php b/core/lib/Drupal/Core/Extension/ThemeInstaller.php
index 70a9eac..2d6567f 100644
--- a/core/lib/Drupal/Core/Extension/ThemeInstaller.php
+++ b/core/lib/Drupal/Core/Extension/ThemeInstaller.php
@@ -7,6 +7,7 @@
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Config\ConfigInstallerInterface;
 use Drupal\Core\Config\ConfigManagerInterface;
+use Drupal\Core\Extension\Exception\UnknownExtensionException;
 use Drupal\Core\Routing\RouteBuilderInterface;
 use Drupal\Core\State\StateInterface;
 use Psr\Log\LoggerInterface;
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index a14f90e..e194c87 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -9,7 +9,7 @@
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Asset\AttachedAssetsInterface;
 use Drupal\Core\Cache\Cache;
-use Drupal\Core\Extension\UnknownExtensionException;
+use Drupal\Core\Extension\Exception\UnknownExtensionException;
 use Drupal\Core\Queue\QueueGarbageCollectionInterface;
 use Drupal\Core\Database\Query\AlterableInterface;
 use Drupal\Core\Extension\Extension;