diff --git a/core/lib/Drupal/Core/Extension/ModuleRequiredByThemesUninstallValidator.php b/core/lib/Drupal/Core/Extension/ModuleRequiredByThemesUninstallValidator.php
index bc44b9ba14..620a8684d1 100644
--- a/core/lib/Drupal/Core/Extension/ModuleRequiredByThemesUninstallValidator.php
+++ b/core/lib/Drupal/Core/Extension/ModuleRequiredByThemesUninstallValidator.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\Core\Extension;
 
-use Drupal\Core\Config\ConfigFactory;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\Core\StringTranslation\TranslationInterface;
 
@@ -27,20 +26,6 @@ class ModuleRequiredByThemesUninstallValidator implements ModuleUninstallValidat
    */
   protected $themeExtensionList;
 
-  /**
-   * The config factory to get the installed themes.
-   *
-   * @var \Drupal\Core\Config\ConfigFactory
-   */
-  protected $configFactory;
-
-  /**
-   * An array of modules that themes depend on.
-   *
-   * @var array
-   */
-  protected $modulesThemesDependOn;
-
   /**
    * Constructs a new ModuleRequiredByThemesUninstallValidator.
    *
@@ -50,15 +35,11 @@ class ModuleRequiredByThemesUninstallValidator implements ModuleUninstallValidat
    *   The module extension list.
    * @param \Drupal\Core\Extension\ThemeExtensionList $extension_list_theme
    *   A extension discovery instance.
-   * @param \Drupal\Core\Config\ConfigFactory $config_factory
-   *   The config factory to get the installed themes.
    */
-  public function __construct(TranslationInterface $string_translation, ModuleExtensionList $extension_list_module, ThemeExtensionList $extension_list_theme = NULL, ConfigFactory $config_factory = NULL) {
+  public function __construct(TranslationInterface $string_translation, ModuleExtensionList $extension_list_module, ThemeExtensionList $extension_list_theme) {
     $this->stringTranslation = $string_translation;
     $this->moduleExtensionList = $extension_list_module;
     $this->themeExtensionList = $extension_list_theme;
-    $this->configFactory = $config_factory;
-    $this->getModulesThemesDependOn();
   }
 
   /**
@@ -67,10 +48,11 @@ public function __construct(TranslationInterface $string_translation, ModuleExte
   public function validate($module) {
     $reasons = [];
 
-    if (isset($this->modulesThemesDependOn[$module])) {
-      $module_name = $this->moduleExtensionList->get($module)->info['name'];
-      $theme_names = implode(", ", $this->modulesThemesDependOn[$module]);
-      $reasons[] = $this->formatPlural(count($theme_names),
+    $modules_themes_depend_on = $this->getModulesThemesDependOn();
+    if (isset($modules_themes_depend_on[$module])) {
+      $module_name = $this->getModuleName($module);
+      $theme_names = implode(", ", $modules_themes_depend_on[$module]);
+      $reasons[] = $this->formatPlural(count($modules_themes_depend_on[$module]),
         'The @module_name module is required by the theme @theme_names',
         'The @module_name module is required by the themes @theme_names',
         ['@module_name' => $module_name, '@theme_names' => $theme_names]);
@@ -79,18 +61,34 @@ public function validate($module) {
     return $reasons;
   }
 
+  /**
+   * Gets the name of a module.
+   *
+   * @param string $module
+   *   The module machine name.
+   *
+   * @return string
+   *   The module name.
+   */
+  protected function getModuleName($module) {
+    return $this->moduleExtensionList->get($module)->info['name'];
+  }
+
   /**
    * Populate $this->modulesThemesDependOn with modules themes depend on.
    */
   protected function getModulesThemesDependOn() {
+    $modules_themes_depend_on = [];
     $installed_themes = $this->themeExtensionList->getAllInstalledInfo();
     foreach ($this->themeExtensionList->getAllInstalledInfo() as $theme) {
       foreach ($theme['dependencies'] as $dependency) {
         if (!isset($installed_themes[$dependency])) {
-          $this->modulesThemesDependOn[$dependency][] = $theme['name'];
+          $modules_themes_depend_on[$dependency][] = $theme['name'];
         }
       }
     }
+
+    return $modules_themes_depend_on;
   }
 
 }
diff --git a/core/lib/Drupal/Core/Extension/RequiredModuleUninstallValidator.php b/core/lib/Drupal/Core/Extension/RequiredModuleUninstallValidator.php
index 096f46d5f5..dc5f999f16 100644
--- a/core/lib/Drupal/Core/Extension/RequiredModuleUninstallValidator.php
+++ b/core/lib/Drupal/Core/Extension/RequiredModuleUninstallValidator.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\Core\Extension;
 
-use Drupal\Core\Config\ConfigFactory;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\Core\StringTranslation\TranslationInterface;
 
@@ -20,20 +19,6 @@ class RequiredModuleUninstallValidator implements ModuleUninstallValidatorInterf
    */
   protected $moduleExtensionList;
 
-  /**
-   * The theme extension list.
-   *
-   * @var \Drupal\Core\Extension\ThemeExtensionList
-   */
-  protected $themeExtensionList;
-
-  /**
-   * The config factory to get the installed themes.
-   *
-   * @var \Drupal\Core\Config\ConfigFactory
-   */
-  protected $configFactory;
-
   /**
    * Constructs a new RequiredModuleUninstallValidator.
    *
@@ -41,26 +26,10 @@ class RequiredModuleUninstallValidator implements ModuleUninstallValidatorInterf
    *   The string translation service.
    * @param \Drupal\Core\Extension\ModuleExtensionList $extension_list_module
    *   The module extension list.
-   * @param \Drupal\Core\Extension\ThemeExtensionList $extension_list_theme
-   *   A extension discovery instance.
-   * @param \Drupal\Core\Config\ConfigFactory $config_factory
-   *   The config factory to get the installed themes.
    */
-  public function __construct(TranslationInterface $string_translation, ModuleExtensionList $extension_list_module, ThemeExtensionList $extension_list_theme = NULL, ConfigFactory $config_factory = NULL) {
+  public function __construct(TranslationInterface $string_translation, ModuleExtensionList $extension_list_module) {
     $this->stringTranslation = $string_translation;
     $this->moduleExtensionList = $extension_list_module;
-
-    if ($extension_list_theme === NULL) {
-      @trigger_error('The extension.list.theme service must be passed to' . __NAMESPACE__ . '\RequiredModuleUninstallValidator::__construct. It was added in Drupal 8.9.0 and will be required before Drupal 9.0.0.', E_USER_DEPRECATED);
-      $extension_list_theme = \Drupal::service('extension.list.theme');
-    }
-    $this->themeExtensionList = $extension_list_theme;
-
-    if ($config_factory === NULL) {
-      @trigger_error('The config.factory service must be passed to' . __NAMESPACE__ . '\RequiredModuleUninstallValidator::__construct. It was added in Drupal 8.9.0 and will be required before Drupal 9.0.0.', E_USER_DEPRECATED);
-      $config_factory = \Drupal::service('config.factory');
-    }
-    $this->configFactory = $config_factory;
   }
 
   /**
@@ -72,10 +41,6 @@ public function validate($module) {
     if (!empty($module_info['required'])) {
       $reasons[] = $this->t('The @module module is required', ['@module' => $module_info['name']]);
     }
-    elseif (!empty($this->getEnabledThemesThatDependOnModule($module))) {
-      $reasons[] = $this->t('The @module module is required', ['@module' => $module_info['name']]);
-    }
-
     return $reasons;
   }
 
@@ -95,20 +60,4 @@ protected function getModuleInfoByModule($module) {
     return [];
   }
 
-  /**
-   * Returns an array of themes that depend on a module.
-   *
-   * @param string $module
-   *   The name of the module.
-   *
-   * @return array
-   *   An array of theme machine names. Empty if no themes depend on the module.
-   */
-  protected function getEnabledThemesThatDependOnModule($module) {
-    $installed_themes = $this->configFactory->get('core.extension')->get('theme');
-    return array_filter(array_keys($installed_themes), function ($theme_name) use ($module) {
-      return isset($this->themeExtensionList->get($theme_name)->module_dependencies[$module]);
-    });
-  }
-
 }
diff --git a/core/lib/Drupal/Core/ProxyClass/Extension/ModuleRequiredByThemesUninstallValidator.php b/core/lib/Drupal/Core/ProxyClass/Extension/ModuleRequiredByThemesUninstallValidator.php
new file mode 100644
index 0000000000..601f482e4d
--- /dev/null
+++ b/core/lib/Drupal/Core/ProxyClass/Extension/ModuleRequiredByThemesUninstallValidator.php
@@ -0,0 +1,88 @@
+<?php
+// @codingStandardsIgnoreFile
+
+/**
+ * This file was generated via php core/scripts/generate-proxy-class.php 'Drupal\Core\Extension\ModuleRequiredByThemesUninstallValidator' "core/lib/Drupal/Core".
+ */
+
+namespace Drupal\Core\ProxyClass\Extension {
+
+    /**
+     * Provides a proxy class for \Drupal\Core\Extension\ModuleRequiredByThemesUninstallValidator.
+     *
+     * @see \Drupal\Component\ProxyBuilder
+     */
+    class ModuleRequiredByThemesUninstallValidator implements \Drupal\Core\Extension\ModuleUninstallValidatorInterface
+    {
+
+        use \Drupal\Core\DependencyInjection\DependencySerializationTrait;
+
+        /**
+         * The id of the original proxied service.
+         *
+         * @var string
+         */
+        protected $drupalProxyOriginalServiceId;
+
+        /**
+         * The real proxied service, after it was lazy loaded.
+         *
+         * @var \Drupal\Core\Extension\ModuleRequiredByThemesUninstallValidator
+         */
+        protected $service;
+
+        /**
+         * The service container.
+         *
+         * @var \Symfony\Component\DependencyInjection\ContainerInterface
+         */
+        protected $container;
+
+        /**
+         * Constructs a ProxyClass Drupal proxy object.
+         *
+         * @param \Symfony\Component\DependencyInjection\ContainerInterface $container
+         *   The container.
+         * @param string $drupal_proxy_original_service_id
+         *   The service ID of the original service.
+         */
+        public function __construct(\Symfony\Component\DependencyInjection\ContainerInterface $container, $drupal_proxy_original_service_id)
+        {
+            $this->container = $container;
+            $this->drupalProxyOriginalServiceId = $drupal_proxy_original_service_id;
+        }
+
+        /**
+         * Lazy loads the real service from the container.
+         *
+         * @return object
+         *   Returns the constructed real service.
+         */
+        protected function lazyLoadItself()
+        {
+            if (!isset($this->service)) {
+                $this->service = $this->container->get($this->drupalProxyOriginalServiceId);
+            }
+
+            return $this->service;
+        }
+
+        /**
+         * {@inheritdoc}
+         */
+        public function validate($module)
+        {
+            return $this->lazyLoadItself()->validate($module);
+        }
+
+        /**
+         * {@inheritdoc}
+         */
+        public function setStringTranslation(\Drupal\Core\StringTranslation\TranslationInterface $translation)
+        {
+            return $this->lazyLoadItself()->setStringTranslation($translation);
+        }
+
+    }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Extension/ModuleRequiredByThemesUninstallValidatorTest.php b/core/tests/Drupal/Tests/Core/Extension/ModuleRequiredByThemesUninstallValidatorTest.php
new file mode 100644
index 0000000000..ed45ac4630
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Extension/ModuleRequiredByThemesUninstallValidatorTest.php
@@ -0,0 +1,96 @@
+<?php
+
+namespace Drupal\Tests\Core\Extension;
+
+use Drupal\Tests\AssertHelperTrait;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\Core\Extension\ModuleRequiredByThemesUninstallValidator
+ * @group Extension
+ */
+class ModuleRequiredByThemesUninstallValidatorTest extends UnitTestCase {
+
+  use AssertHelperTrait;
+
+  /**
+   * The PHPUnit mock of ModuleRequiredByThemesUninstallValidator.
+   *
+   * @var \Drupal\Core\Extension\ModuleRequiredByThemesUninstallValidator|\PHPUnit\Framework\MockObject\MockObject
+   */
+  protected $moduleRequiredByThemeUninstallValidator;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->moduleRequiredByThemeUninstallValidator = $this->getMockBuilder('Drupal\Core\Extension\ModuleRequiredByThemesUninstallValidator')
+      ->disableOriginalConstructor()
+      ->setMethods(['getModulesThemesDependOn', 'getModuleName'])
+      ->getMock();
+    $this->moduleRequiredByThemeUninstallValidator->setStringTranslation($this->getStringTranslationStub());
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateNoThemeDependency() {
+    $this->moduleRequiredByThemeUninstallValidator->expects($this->once())
+      ->method('getModulesThemesDependOn')
+      ->willReturn([]);
+
+    $module = $this->randomMachineName();
+    $expected = [];
+    $reasons = $this->moduleRequiredByThemeUninstallValidator->validate($module);
+    $this->assertSame($expected, $reasons);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateOneThemeDependency() {
+    $module = 'single_module';
+    $module_name = 'Single Module';
+    $theme_name = 'One Theme';
+    $this->moduleRequiredByThemeUninstallValidator->expects($this->once())
+      ->method('getModulesThemesDependOn')
+      ->willReturn([
+        $module => [$theme_name],
+      ]);
+    $this->moduleRequiredByThemeUninstallValidator->expects($this->once())
+      ->method('getModuleName')
+      ->willReturn($module_name);
+
+    $expected = [
+      "The $module_name module is required by the theme $theme_name",
+    ];
+    $reasons = $this->moduleRequiredByThemeUninstallValidator->validate($module);
+    $this->assertSame($expected, $this->castSafeStrings($reasons));
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateTwoThemeDependencies() {
+    $module = 'popular_module';
+    $module_name = 'Popular Module';
+    $theme_name_1 = 'First Theme';
+    $theme_name_2 = 'Second Theme';
+    $this->moduleRequiredByThemeUninstallValidator->expects($this->once())
+      ->method('getModulesThemesDependOn')
+      ->willReturn([
+        $module => [$theme_name_1, $theme_name_2],
+      ]);
+    $this->moduleRequiredByThemeUninstallValidator->expects($this->once())
+      ->method('getModuleName')
+      ->willReturn($module_name);
+
+    $expected = [
+      "The $module_name module is required by the themes $theme_name_1, $theme_name_2",
+    ];
+    $reasons = $this->moduleRequiredByThemeUninstallValidator->validate($module);
+    $this->assertSame($expected, $this->castSafeStrings($reasons));
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Extension/RequiredModuleUninstallValidatorTest.php b/core/tests/Drupal/Tests/Core/Extension/RequiredModuleUninstallValidatorTest.php
index e00a1435d5..a22a42eb91 100644
--- a/core/tests/Drupal/Tests/Core/Extension/RequiredModuleUninstallValidatorTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/RequiredModuleUninstallValidatorTest.php
@@ -25,7 +25,7 @@ protected function setUp() {
     parent::setUp();
     $this->uninstallValidator = $this->getMockBuilder('Drupal\Core\Extension\RequiredModuleUninstallValidator')
       ->disableOriginalConstructor()
-      ->setMethods(['getModuleInfoByModule', 'getEnabledThemesThatDependOnModule'])
+      ->setMethods(['getModuleInfoByModule'])
       ->getMock();
     $this->uninstallValidator->setStringTranslation($this->getStringTranslationStub());
   }