diff --git a/sapi/cli/tests/php_cli_server.inc b/sapi/cli/tests/php_cli_server.inc
index 3ad6ced5cb44..feee2bbb5686 100644
--- a/sapi/cli/tests/php_cli_server.inc
+++ b/sapi/cli/tests/php_cli_server.inc
@@ -16,8 +16,8 @@ function php_cli_server_start(
     $php_executable = getenv('TEST_PHP_EXECUTABLE') ?: PHP_BINARY;
     $error = null;
 
-    // Create dedicated doc root to avoid index.php clashes between tests.
-    $doc_root = __DIR__ . DIRECTORY_SEPARATOR . basename($_SERVER['PHP_SELF'], '.php');
+    // Create dedicated doc root to avoid index.php clashes between processes.
+    $doc_root = __DIR__ . DIRECTORY_SEPARATOR . basename($_SERVER['PHP_SELF'], '.php') . '-' . getmypid();
     @mkdir($doc_root);
 
     if ($code) {
diff --git a/sapi/cli/tests/php_cli_server_002.phpt b/sapi/cli/tests/php_cli_server_002.phpt
index d2b561b8bb6b..e3204c06ee8d 100644
--- a/sapi/cli/tests/php_cli_server_002.phpt
+++ b/sapi/cli/tests/php_cli_server_002.phpt
@@ -13,7 +13,7 @@ php_cli_server_start('var_dump($_SERVER["DOCUMENT_ROOT"], $_SERVER["SERVER_SOFTW
 var_dump(file_get_contents("http://" . PHP_CLI_SERVER_ADDRESS));
 ?>
 --EXPECTF--
-string(%d) "string(%d) "%sphp_cli_server_002"
+string(%d) "string(%d) "%sphp_cli_server_002-%d"
 string(%d) "PHP/%s (Development Server)"
 string(%d) "localhost"
 string(%d) "%s"