@@ -13,6 +13,7 @@
 from test.support import os_helper
 from test.support.script_helper import assert_python_ok, assert_python_failure
 from test.support import threading_helper
+from test.support import import_helper
 import textwrap
 import unittest
 import warnings
@@ -994,6 +995,15 @@ def test_module_names(self):
         for name in sys.stdlib_module_names:
             self.assertIsInstance(name, str)
 
+    def test_stdlib_dir(self):
+        os = import_helper.import_fresh_module('os')
+        marker = getattr(os, '__file__', None)
+        if marker and not os.path.exists(marker):
+            marker = None
+        expected = os.path.dirname(marker) if marker else None
+        actual = sys._stdlib_dir
+        self.assertEqual(actual, expected)
+
 
 @test.support.cpython_only
 class UnraisableHookTest(unittest.TestCase):
 
@@ -2974,6 +2974,14 @@ _PySys_UpdateConfig(PyThreadState *tstate)
 
     SET_SYS("_xoptions", sys_create_xoptions_dict(config));
 
+    const wchar_t *stdlibdir = _Py_GetStdlibDir();
+    if (stdlibdir != NULL) {
+        SET_SYS_FROM_WSTR("_stdlib_dir", stdlibdir);
+    }
+    else {
+        PyDict_SetItemString(sysdict, "_stdlib_dir", Py_None);
+    }
+
 #undef SET_SYS_FROM_WSTR
 #undef COPY_LIST
 #undef COPY_WSTR