core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php | 2 --
 1 file changed, 2 deletions(-)

diff --git a/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php b/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
index 94f343f625..8b050f749b 100644
--- a/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
+++ b/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
@@ -442,8 +442,6 @@ protected function installDefaultThemeFromClassProperty(ContainerInterface $cont
     $system_theme_config = $container->get('config.factory')->getEditable('system.theme');
     if ($system_theme_config->get('default') !== $this->defaultTheme) {
       $system_theme_config
-        // @see core/modules/system/config/install/system.theme.yml
-        ->clear('admin')
         ->set('default', $this->defaultTheme)
         ->save();
     }