diff --git a/core/tests/Drupal/KernelTests/KernelTestBase.php b/core/tests/Drupal/KernelTests/KernelTestBase.php
index 3e54b3f085..32c97b63b5 100644
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -324,10 +324,10 @@ public function getDatabasePrefix() {
   private function bootKernel() {
     $this->setSetting('container_yamls', []);
     // Allow for test-specific overrides.
-    $settings_services_file = $this->root . '/sites/default' . '/testing.services.yml';
+    $settings_services_file = $this->root . '/sites/default/testing.services.yml';
     if (file_exists($settings_services_file)) {
       // Copy the testing-specific service overrides in place.
-      $testing_services_file = $this->root . '/' . $this->siteDirectory . '/services.yml';
+      $testing_services_file = $this->siteDirectory . '/services.yml';
       copy($settings_services_file, $testing_services_file);
       $this->setSetting('container_yamls', [$testing_services_file]);
     }