diff -u b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldValuesTest.php b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldValuesTest.php
--- b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldValuesTest.php
+++ b/core/modules/layout_builder/tests/src/FunctionalJavascript/FieldValuesTest.php
@@ -27,6 +27,11 @@
   /**
    * {@inheritdoc}
    */
+  protected $defaultTheme = 'classy';
+
+  /**
+   * {@inheritdoc}
+   */
   protected function setUp() {
     parent::setUp();