--- a/mercurial/exewrapper.c	Thu May 20 19:59:03 2021 -0400
+++ b/mercurial/exewrapper.c	Tue May 11 01:05:38 2021 -0400
@@ -48,7 +48,7 @@
 	int(__cdecl * Py_Main)(int argc, TCHAR *argv[]);
 
 #if PY_MAJOR_VERSION >= 3
-	Py_LegacyWindowsStdioFlag = 1;
+	_wputenv(L"PYTHONLEGACYWINDOWSSTDIO=1");
 #endif
 
 	if (GetModuleFileName(NULL, pyscript, _countof(pyscript)) == 0) {