diff --git a/ox/form.py b/ox/form.py
index 5358afb..faa1551 100644
--- a/ox/form.py
+++ b/ox/form.py
@@ -5,7 +5,8 @@ from __future__ import print_function
 
 import itertools
 import mimetypes
-import random
+import os
+import hashlib
 import sys
 
 from six import PY2
@@ -20,8 +21,7 @@ _fmt = '%%0%dd' % _width
 
 def _make_boundary():
     # Craft a random boundary.
-    token = random.randrange(sys.maxsize)
-    boundary = ('=' * 15) + (_fmt % token) + '=='
+    boundary = ('=' * 15) + hashlib.sha1(os.urandom(32)).hexdigest() + '=='
     return boundary
 
 class MultiPartForm(object):