tests/src/Functional/CdnIntegrationTest.php | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tests/src/Functional/CdnIntegrationTest.php b/tests/src/Functional/CdnIntegrationTest.php
index 5899d27..597367a 100644
--- a/tests/src/Functional/CdnIntegrationTest.php
+++ b/tests/src/Functional/CdnIntegrationTest.php
@@ -21,6 +21,11 @@ class CdnIntegrationTest extends BrowserTestBase {
    */
   public static $modules = ['node', 'cdn', 'file', 'editor'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   /**
    * {@inheritdoc}
    */
@@ -130,7 +135,7 @@ class CdnIntegrationTest extends BrowserTestBase {
   protected function assertCssFileUsesRootRelativeUrl($css_file_url) {
     $this->drupalGet($css_file_url);
     $this->assertSession()->responseContains('url(', 'CSS references other files.');
-    $this->assertSession()->responseContains('url(' . base_path() . 'core/themes/stable/images/core/tree.png)', 'CSS references other files by root-relative URL, not CDN URL.');
+    $this->assertSession()->responseContains('url(' . base_path() . 'core/misc/tree.png)', 'CSS references other files by root-relative URL, not CDN URL.');
   }
 
   /**