core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php b/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
index 176b6f37f3..b05c05d39c 100644
--- a/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
+++ b/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
@@ -365,6 +365,12 @@ protected function initConfig(ContainerInterface $container) {
     if (empty($this->theme)) {
       @trigger_error('Drupal\Tests\BrowserTestBase::$theme is required in drupal:9.0.0. See https://www.drupal.org/node/2352949', E_USER_DEPRECATED);
       $this->theme = 'classy';
+      if ($this->profile === 'demo_umami') {
+        $this->theme = 'umami';
+      }
+      elseif ($this->profile === 'standard') {
+        $this->theme = 'bartik';
+      }
     }
     $config->getEditable('system.theme')
       ->set('default', $this->theme)