--- a/cubicweb/test/unittest_utils.py	Wed Oct 12 11:09:08 2016 +0200
+++ b/cubicweb/test/unittest_utils.py	Wed Oct 12 11:07:10 2016 +0200
@@ -17,15 +17,19 @@
 # with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
 """unit tests for module cubicweb.utils"""
 
+import base64
 import datetime
 import decimal
 import doctest
 import re
+try:
+    from unittest2 import TestCase
+except ImportError:  # Python3
+    from unittest import TestCase
 
 from six.moves import range
 
-from logilab.common.testlib import TestCase, unittest_main
-
+from cubicweb import Binary
 from cubicweb.devtools.testlib import CubicWebTC
 from cubicweb.utils import (make_uid, UStringIO, RepeatList, HTMLHead,
                             QueryCache, parse_repo_uri)
@@ -200,6 +204,12 @@
         self.assertEqual(json.loads(self.encode([e])),
                           [{'pouet': 'hop', 'eid': 2}])
 
+    def test_encoding_binary(self):
+        for content in (b'he he', b'h\xe9 hxe9'):
+            with self.subTest(content=content):
+                encoded = self.encode(Binary(content))
+                self.assertEqual(base64.b64decode(encoded), content)
+
     def test_encoding_unknown_stuff(self):
         self.assertEqual(self.encode(TestCase), 'null')
 
@@ -322,4 +332,5 @@
 
 
 if __name__ == '__main__':
-    unittest_main()
+    import unittest
+    unittest.main()

--- a/cubicweb/utils.py	Wed Oct 12 11:09:08 2016 +0200
+++ b/cubicweb/utils.py	Wed Oct 12 11:07:10 2016 +0200
@@ -21,6 +21,7 @@
 
 __docformat__ = "restructuredtext en"
 
+import base64
 import decimal
 import datetime
 import random
@@ -42,6 +43,9 @@
 from logilab.common.deprecation import deprecated
 from logilab.common.date import ustrftime
 
+from cubicweb import Binary
+
+
 _MARKER = object()
 
 # initialize random seed from current time
@@ -507,6 +511,8 @@
             return (obj.days * 24 * 60 * 60) + obj.seconds
         elif isinstance(obj, decimal.Decimal):
             return float(obj)
+        elif isinstance(obj, Binary):
+            return base64.b64encode(obj.getvalue()).decode('ascii')
         try:
             return json.JSONEncoder.default(self, obj)
         except TypeError: