If MS_WIN64 is defined, MS_WINDOWS is also defined: #ifdef can be simplified.
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 3a31314..e0c5bfe 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -390,7 +390,7 @@
 
     Py_BEGIN_ALLOW_THREADS
     errno = 0;
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
     if (n > INT_MAX)
         n = INT_MAX;
     n = write(self->fd, c, (int)n);