diff --git a/core/tests/Drupal/KernelTests/Core/Common/LegacyFunctionsTest.php b/core/tests/Drupal/KernelTests/Core/Common/LegacyFunctionsTest.php
index ad141340ff..b53f162dbd 100644
--- a/core/tests/Drupal/KernelTests/Core/Common/LegacyFunctionsTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Common/LegacyFunctionsTest.php
@@ -43,7 +43,7 @@ public function _testArchiverGetExtensions() {
    * @expectedDeprecation archiver_get_archiver() is deprecated in Drupal 8.7.0 and will be removed in Drupal 9.0.x. Instead, get plugin.manager.archiver service from container and call getInstance() method on it. For example $archiver->getInstance(["filepath" => $file]); See https://www.drupal.org/node/2999951
    */
   public function testArchiverGetArchiver() {
-    $file = DRUPAL_ROOT . 'core/modules/update/tests/aaa_update_test.tar.gz';
+    $file = DRUPAL_ROOT . '/core/modules/update/tests/aaa_update_test.tar.gz';
     $expected = \Drupal::service('plugin.manager.archiver')->getInstance([
       'filepath' => $file,
     ]);