diff -u b/core/profiles/testing_inherited_standard/tests/src/Functional/InheritedProfileTest.php b/core/profiles/testing_inherited_standard/tests/src/Functional/InheritedProfileTest.php
--- b/core/profiles/testing_inherited_standard/tests/src/Functional/InheritedProfileTest.php
+++ b/core/profiles/testing_inherited_standard/tests/src/Functional/InheritedProfileTest.php
@@ -17,6 +17,11 @@
   protected $profile = 'testing_inherited_standard';
 
   /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stable';
+
+  /**
    * Tests inherited installation profile.
    */
   public function testInheritedProfile() {
only in patch2:
unchanged:
--- /dev/null
+++ b/core/profiles/testing_subsubprofile/config/install/system.theme.yml
@@ -0,0 +1,2 @@
+# @todo: Remove this file once https://www.drupal.org/node/2854576 is resolved.
+default: stable