diff --git a/Python/fileutils.c b/Python/fileutils.c
@@ -2138,7 +2138,9 @@ wchar_t *
_Py_join_relfile(const wchar_t *dirname, const wchar_t *relfile)
{
    assert(dirname != NULL && relfile != NULL);
    assert(!_Py_isabs(relfile));
    size_t maxlen = wcslen(dirname) + 1 + wcslen(relfile);
    size_t bufsize = maxlen + 1;
    wchar_t *filename = PyMem_RawMalloc(bufsize * sizeof(wchar_t));