diff --git a/Python/fileutils.c b/Python/fileutils.c
index a38886a17ccbbe..7e5d01f6e63d3b 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -603,9 +603,9 @@ _Py_DecodeLocaleEx(const char* arg, wchar_t **wstr, size_t *wlen,
     return _Py_DecodeUTF8Ex(arg, strlen(arg), wstr, wlen, reason,
                             errors);
 #else
-    int use_utf8 = (Py_UTF8Mode == 1);
+    int use_utf8 = (_PyRuntime.preconfig.utf8_mode >= 1);
 #ifdef MS_WINDOWS
-    use_utf8 |= !Py_LegacyWindowsFSEncodingFlag;
+    use_utf8 |= (_PyRuntime.preconfig.legacy_windows_fs_encoding == 0);
 #endif
     if (use_utf8) {
         return _Py_DecodeUTF8Ex(arg, strlen(arg), wstr, wlen, reason,
@@ -795,9 +795,9 @@ encode_locale_ex(const wchar_t *text, char **str, size_t *error_pos,
     return _Py_EncodeUTF8Ex(text, str, error_pos, reason,
                             raw_malloc, errors);
 #else
-    int use_utf8 = (Py_UTF8Mode == 1);
+    int use_utf8 = (_PyRuntime.preconfig.utf8_mode >= 1);
 #ifdef MS_WINDOWS
-    use_utf8 |= !Py_LegacyWindowsFSEncodingFlag;
+    use_utf8 |= (_PyRuntime.preconfig.legacy_windows_fs_encoding == 0);
 #endif
     if (use_utf8) {
         return _Py_EncodeUTF8Ex(text, str, error_pos, reason,
diff --git a/Python/preconfig.c b/Python/preconfig.c
index afa16cccf32e96..e7125cd2e3e0e3 100644
--- a/Python/preconfig.c
+++ b/Python/preconfig.c
@@ -826,12 +826,10 @@ _PyPreConfig_Read(PyPreConfig *config, const _PyArgv *args)
         _Py_SetLocaleFromEnv(LC_CTYPE);
     }
 
-    _PyPreCmdline cmdline = _PyPreCmdline_INIT;
-    int init_utf8_mode = Py_UTF8Mode;
-#ifdef MS_WINDOWS
-    int init_legacy_encoding = Py_LegacyWindowsFSEncodingFlag;
-#endif
+    PyPreConfig save_runtime_config;
+    preconfig_copy(&save_runtime_config, &_PyRuntime.preconfig);
 
+    _PyPreCmdline cmdline = _PyPreCmdline_INIT;
     int locale_coerced = 0;
     int loops = 0;
 
@@ -847,11 +845,9 @@ _PyPreConfig_Read(PyPreConfig *config, const _PyArgv *args)
         }
 
         /* bpo-34207: Py_DecodeLocale() and Py_EncodeLocale() depend
-           on Py_UTF8Mode and Py_LegacyWindowsFSEncodingFlag. */
-        Py_UTF8Mode = config->utf8_mode;
-#ifdef MS_WINDOWS
-        Py_LegacyWindowsFSEncodingFlag = config->legacy_windows_fs_encoding;
-#endif
+           on the utf8_mode and legacy_windows_fs_encoding members
+           of _PyRuntime.preconfig. */
+        preconfig_copy(&_PyRuntime.preconfig, config);
 
         if (args) {
             // Set command line arguments at each iteration. If they are bytes
@@ -914,14 +910,10 @@ _PyPreConfig_Read(PyPreConfig *config, const _PyArgv *args)
     status = _PyStatus_OK();
 
 done:
-    if (init_ctype_locale != NULL) {
-        setlocale(LC_CTYPE, init_ctype_locale);
-        PyMem_RawFree(init_ctype_locale);
-    }
-    Py_UTF8Mode = init_utf8_mode ;
-#ifdef MS_WINDOWS
-    Py_LegacyWindowsFSEncodingFlag = init_legacy_encoding;
-#endif
+    // Revert side effects
+    setlocale(LC_CTYPE, init_ctype_locale);
+    PyMem_RawFree(init_ctype_locale);
+    preconfig_copy(&_PyRuntime.preconfig, &save_runtime_config);
     _PyPreCmdline_Clear(&cmdline);
     return status;
 }