diff --git a/core/lib/Drupal/Core/Extension/ModuleHandler.php b/core/lib/Drupal/Core/Extension/ModuleHandler.php
index f48116c..8e1853b 100644
--- a/core/lib/Drupal/Core/Extension/ModuleHandler.php
+++ b/core/lib/Drupal/Core/Extension/ModuleHandler.php
@@ -5,6 +5,7 @@
 use Drupal\Component\Graph\Graph;
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Extension\Exception\UnknownExtensionException;
 
 /**
  * Class that manages modules in a Drupal installation.
diff --git a/core/lib/Drupal/Core/Extension/ModuleHandlerInterface.php b/core/lib/Drupal/Core/Extension/ModuleHandlerInterface.php
index 35cb5c5..abb4edd 100644
--- a/core/lib/Drupal/Core/Extension/ModuleHandlerInterface.php
+++ b/core/lib/Drupal/Core/Extension/ModuleHandlerInterface.php
@@ -61,7 +61,7 @@ public function getModuleList();
    * @return \Drupal\Core\Extension\Extension
    *   An extension object.
    *
-   * @throws \Drupal\Core\Extension\UnknownExtensionException
+   * @throws \Drupal\Core\Extension\Exception\UnknownExtensionException
    *   Thrown when the requested module does not exist.
    */
   public function getModule($name);
diff --git a/core/lib/Drupal/Core/Extension/ThemeHandler.php b/core/lib/Drupal/Core/Extension/ThemeHandler.php
index c83477d..4258fda 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandler.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandler.php
@@ -4,6 +4,7 @@
 
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Extension\Exception\UninstalledExtensionException;
+use Drupal\Core\Extension\Exception\UnknownExtensionException;
 use Drupal\Core\State\StateInterface;
 
 /**
diff --git a/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php b/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
index f25666d..882faf5 100644
--- a/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
+++ b/core/lib/Drupal/Core/Extension/ThemeHandlerInterface.php
@@ -148,7 +148,7 @@ public function getBaseThemes(array $themes, $theme);
    * @return string
    *   Returns the human readable name of the theme.
    *
-   * @throws \Drupal\Core\Extension\UnknownExtensionException
+   * @throws \Drupal\Core\Extension\Exception\UnknownExtensionException
    *   When the specified theme does not exist.
    */
   public function getName($theme);
@@ -210,7 +210,7 @@ public function themeExists($theme);
    * @return \Drupal\Core\Extension\Extension
    *   An extension object.
    *
-   * @throws \Drupal\Core\Extension\UnknownExtensionException
+   * @throws \Drupal\Core\Extension\Extension\UnknownExtensionException
    *   Thrown when the requested theme does not exist.
    */
   public function getTheme($name);
diff --git a/core/lib/Drupal/Core/Extension/ThemeInstallerInterface.php b/core/lib/Drupal/Core/Extension/ThemeInstallerInterface.php
index ff9b95e..ae79b50 100644
--- a/core/lib/Drupal/Core/Extension/ThemeInstallerInterface.php
+++ b/core/lib/Drupal/Core/Extension/ThemeInstallerInterface.php
@@ -23,7 +23,7 @@
    * @throws \Drupal\Core\Extension\ExtensionNameLengthException
    *   Thrown when the theme name is to long.
    *
-   * @throws \Drupal\Core\Extension\UnknownExtensionException
+   * @throws \Drupal\Core\Extension\Exception\UnknownExtensionException
    *   Thrown when the theme does not exist.
    */
   public function install(array $theme_list, $install_dependencies = TRUE);
@@ -37,7 +37,7 @@ public function install(array $theme_list, $install_dependencies = TRUE);
    * @param array $theme_list
    *   The themes to uninstall.
    *
-   * @throws \Drupal\Core\Extension\UnknownExtensionException
+   * @throws \Drupal\Core\Extension\Exception\UnknownExtensionException
    *   Thrown when trying to uninstall a theme that was not installed.
    *
    * @throws \InvalidArgumentException