diff --git a/tools/python/xen/lowlevel/xc/xc.c b/tools/python/xen/lowlevel/xc/xc.c
index fd00861032..cfb2734a99 100644
--- a/tools/python/xen/lowlevel/xc/xc.c
+++ b/tools/python/xen/lowlevel/xc/xc.c
@@ -4,6 +4,7 @@
  * Copyright (c) 2003-2004, K A Fraser (University of Cambridge)
  */
 
+#define PY_SSIZE_T_CLEAN
 #include <Python.h>
 #define XC_WANT_COMPAT_MAP_FOREIGN_API
 #include <xenctrl.h>
@@ -1774,7 +1775,7 @@ static PyObject *pyflask_load(PyObject *self, PyObject *args, PyObject *kwds)
 {
     xc_interface *xc_handle;
     char *policy;
-    uint32_t len;
+    Py_ssize_t len;
     int ret;
 
     static char *kwd_list[] = { "policy", NULL };
diff --git a/tools/python/xen/lowlevel/xs/xs.c b/tools/python/xen/lowlevel/xs/xs.c
index 0dad7fa5f2..3ba5a8b893 100644
--- a/tools/python/xen/lowlevel/xs/xs.c
+++ b/tools/python/xen/lowlevel/xs/xs.c
@@ -18,6 +18,7 @@
  * Copyright (C) 2005 XenSource Ltd.
  */
 
+#define PY_SSIZE_T_CLEAN
 #include <Python.h>
 
 #include <stdbool.h>
@@ -141,7 +142,7 @@ static PyObject *xspy_write(XsHandle *self, PyObject *args)
     char *thstr;
     char *path;
     char *data;
-    int data_n;
+    Py_ssize_t data_n;
     bool result;
 
     if (!xh)