diff --git a/tests/PHPStan/Rules/Keywords/data/require-file-simple-case.php b/tests/PHPStan/Rules/Keywords/data/require-file-simple-case.php
index a0d03a39c2b..4e31bb0d051 100644
--- a/tests/PHPStan/Rules/Keywords/data/require-file-simple-case.php
+++ b/tests/PHPStan/Rules/Keywords/data/require-file-simple-case.php
@@ -1,6 +1,6 @@
 <?php declare(strict_types=1);
 
-$fileThatExists = __DIR__ . '/include-me-to-prove-you-work.txt';
+$fileThatExists = __DIR__ . DIRECTORY_SEPARATOR . 'include-me-to-prove-you-work.txt';
 $fileThatDoesNotExist = 'a-file-that-does-not-exist.php';
 
 include $fileThatExists;