If MS_WIN64 is defined, MS_WINDOWS is also defined: #ifdef can be simplified.
diff --git a/Modules/_io/_iomodule.h b/Modules/_io/_iomodule.h
index 0fe90a3..ad1faa8 100644
--- a/Modules/_io/_iomodule.h
+++ b/Modules/_io/_iomodule.h
@@ -77,7 +77,7 @@
    long with "%lld" even when both long and long long have the same
    precision. */
 
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
 
 /* Windows uses long long for offsets */
 typedef PY_LONG_LONG Py_off_t;
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
index 34a5801..efcc594 100644
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -533,7 +533,7 @@
         len = pbuf.len;
         Py_BEGIN_ALLOW_THREADS
         errno = 0;
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
         if (len > INT_MAX)
             len = INT_MAX;
         n = read(self->fd, pbuf.buf, (int)len);
@@ -602,7 +602,7 @@
     if (!_PyVerify_fd(self->fd))
         return PyErr_SetFromErrno(PyExc_IOError);
 
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
     pos = _lseeki64(self->fd, 0L, SEEK_CUR);
 #else
     pos = lseek(self->fd, 0L, SEEK_CUR);
@@ -645,7 +645,7 @@
         Py_BEGIN_ALLOW_THREADS
         errno = 0;
         n = bufsize - bytes_read;
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
         if (n > INT_MAX)
             n = INT_MAX;
         n = read(self->fd, PyBytes_AS_STRING(result) + bytes_read, (int)n);
@@ -706,7 +706,7 @@
         return fileio_readall(self);
     }
 
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
     if (size > INT_MAX)
         size = INT_MAX;
 #endif
@@ -718,7 +718,7 @@
     if (_PyVerify_fd(self->fd)) {
         Py_BEGIN_ALLOW_THREADS
         errno = 0;
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
         n = read(self->fd, ptr, (int)size);
 #else
         n = read(self->fd, ptr, size);
@@ -766,7 +766,7 @@
         Py_BEGIN_ALLOW_THREADS
         errno = 0;
         len = pbuf.len;
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
         if (len > 32767 && isatty(self->fd)) {
             /* Issue #11395: the Windows console returns an error (12: not
                enough space error) on writing into stdout if stdout mode is
@@ -839,7 +839,7 @@
 
     if (_PyVerify_fd(fd)) {
         Py_BEGIN_ALLOW_THREADS
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
         res = _lseeki64(fd, pos, whence);
 #else
         res = lseek(fd, pos, whence);
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index baad299..fd4628c 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -361,7 +361,7 @@
 #undef STAT
 #undef FSTAT
 #undef STRUCT_STAT
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
 #       define STAT win32_stat
 #       define LSTAT win32_lstat
 #       define FSTAT win32_fstat
@@ -7425,7 +7425,7 @@
 posix_lseek(PyObject *self, PyObject *args)
 {
     int fd, how;
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
     PY_LONG_LONG pos, res;
 #else
     off_t pos, res;
@@ -7453,7 +7453,7 @@
     if (!_PyVerify_fd(fd))
         return posix_error();
     Py_BEGIN_ALLOW_THREADS
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
     res = _lseeki64(fd, pos, how);
 #else
     res = lseek(fd, pos, how);
@@ -7659,7 +7659,7 @@
     }
     len = pbuf.len;
     Py_BEGIN_ALLOW_THREADS
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
     if (len > INT_MAX)
         len = INT_MAX;
     size = write(fd, pbuf.buf, (int)len);
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index bd0a20a..0fd14ab 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -2553,7 +2553,7 @@
     Py_BEGIN_ALLOW_THREADS
     timeout = internal_select_ex(s, 0, interval);
     if (!timeout) {
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
         if (len > INT_MAX)
             len = INT_MAX;
         outlen = recv(s->sock_fd, cbuf, (int)len, flags);
@@ -3251,7 +3251,7 @@
     if (!timeout) {
 #ifdef __VMS
         n = sendsegmented(s->sock_fd, buf, len, flags);
-#elif defined(MS_WIN64) || defined(MS_WINDOWS)
+#elif defined(MS_WINDOWS)
         if (len > INT_MAX)
             len = INT_MAX;
         n = send(s->sock_fd, buf, (int)len, flags);
@@ -3308,7 +3308,7 @@
         if (!timeout) {
 #ifdef __VMS
             n = sendsegmented(s->sock_fd, buf, len, flags);
-#elif defined(MS_WIN64) || defined(MS_WINDOWS)
+#elif defined(MS_WINDOWS)
             if (len > INT_MAX)
                 len = INT_MAX;
             n = send(s->sock_fd, buf, (int)len, flags);
@@ -3407,7 +3407,7 @@
     Py_BEGIN_ALLOW_THREADS
     timeout = internal_select_ex(s, 1, interval);
     if (!timeout) {
-#if defined(MS_WIN64) || defined(MS_WINDOWS)
+#ifdef MS_WINDOWS
         if (len > INT_MAX)
             len = INT_MAX;
         n = sendto(s->sock_fd, buf, (int)len, flags,