diff --git a/tests/src/Functional/WebformBrowserTestBase.php b/tests/src/Functional/WebformBrowserTestBase.php
index 05a61acb5..cbf28bcd8 100644
--- a/tests/src/Functional/WebformBrowserTestBase.php
+++ b/tests/src/Functional/WebformBrowserTestBase.php
@@ -35,6 +35,7 @@ abstract class WebformBrowserTestBase extends BrowserTestBase {
    */
   public function setUp() {
     parent::setUp();
+    $this->initializeThemes();
     $this->loadWebforms(static::$testWebforms);
   }
 
diff --git a/tests/src/FunctionalJavascript/WebformWebDriverTestBase.php b/tests/src/FunctionalJavascript/WebformWebDriverTestBase.php
index 479d2d8e1..6f1d453d9 100644
--- a/tests/src/FunctionalJavascript/WebformWebDriverTestBase.php
+++ b/tests/src/FunctionalJavascript/WebformWebDriverTestBase.php
@@ -35,6 +35,7 @@ abstract class WebformWebDriverTestBase extends WebDriverTestBase {
    */
   public function setUp() {
     parent::setUp();
+    $this->initializeThemes();
     $this->loadWebforms(static::$testWebforms);
   }
 
diff --git a/tests/src/Traits/WebformBrowserTestTrait.php b/tests/src/Traits/WebformBrowserTestTrait.php
index b29ea53be..fbe5c42b7 100644
--- a/tests/src/Traits/WebformBrowserTestTrait.php
+++ b/tests/src/Traits/WebformBrowserTestTrait.php
@@ -18,6 +18,40 @@ use Drupal\webform\Entity\Webform;
  */
 trait WebformBrowserTestTrait {
 
+  /**
+   * Default theme.
+   *
+   * @var string
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Default admin theme.
+   *
+   * @var string
+   */
+  protected $adminTheme;
+
+  /**
+   * Initialize default and admin themes.
+   */
+  protected function initializeThemes() {
+    $theme_handler = $this->container->get('theme_handler');
+    if ($this->defaultTheme) {
+      $theme_handler->install([$this->defaultTheme]);
+      $this->config('system.theme')
+        ->set('default', $this->defaultTheme)
+        ->save();
+
+    }
+    if ($this->adminTheme) {
+      $theme_handler->install([$this->adminTheme]);
+      $this->config('system.theme')
+        ->set('admin', $this->adminTheme)
+        ->save();
+    }
+  }
+
   /****************************************************************************/
   // Block.
   /****************************************************************************/