diff --git a/docs/api.rst b/docs/api.rst
index 291bfabb..27333079 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -224,6 +224,18 @@ implementation that Flask is using.
 .. autoclass:: SessionMixin
    :members:
 
+.. autodata:: session_json_serializer
+
+   This object provides dumping and loading methods similar to simplejson
+   but it also tags certain builtin Python objects that commonly appear in
+   sessions.  Currently the following extended values are supported in
+   the JSON it dumps:
+
+   -    :class:`~markupsafe.Markup` objects
+   -    :class:`~uuid.UUID` objects
+   -    :class:`~datetime.datetime` objects
+   -   :class:`tuple`\s
+
 .. admonition:: Notice
 
    The ``PERMANENT_SESSION_LIFETIME`` config key can also be an integer
diff --git a/flask/sessions.py b/flask/sessions.py
index 4a156d36..31b5900b 100644
--- a/flask/sessions.py
+++ b/flask/sessions.py
@@ -9,6 +9,7 @@
     :license: BSD, see LICENSE for more details.
 """
 
+import uuid
 import hashlib
 from datetime import datetime
 from werkzeug.http import http_date, parse_date
@@ -58,6 +59,8 @@ class TaggedJSONSerializer(object):
         def _tag(value):
             if isinstance(value, tuple):
                 return {' t': [_tag(x) for x in value]}
+            elif isinstance(value, uuid.UUID):
+                return {' u': value.hex}
             elif callable(getattr(value, '__html__', None)):
                 return {' m': unicode(value.__html__())}
             elif isinstance(value, list):
@@ -84,6 +87,8 @@ class TaggedJSONSerializer(object):
             the_key, the_value = obj.iteritems().next()
             if the_key == ' t':
                 return tuple(the_value)
+            elif the_key == ' u':
+                return uuid.UUID(the_value)
             elif the_key == ' m':
                 return Markup(the_value)
             elif the_key == ' d':
diff --git a/flask/testsuite/basic.py b/flask/testsuite/basic.py
index 445b6b41..5f6dbe4b 100644
--- a/flask/testsuite/basic.py
+++ b/flask/testsuite/basic.py
@@ -12,6 +12,7 @@
 from __future__ import with_statement
 
 import re
+import uuid
 import flask
 import pickle
 import unittest
@@ -319,10 +320,12 @@ class BasicFunctionalityTestCase(FlaskTestCase):
         app.secret_key = 'development-key'
         app.testing = True
         now = datetime.utcnow().replace(microsecond=0)
+        the_uuid = uuid.uuid4()
 
         @app.after_request
         def modify_session(response):
             flask.session['m'] = flask.Markup('Hello!')
+            flask.session['u'] = the_uuid
             flask.session['dt'] = now
             flask.session['t'] = (1, 2, 3)
             return response
@@ -337,6 +340,7 @@ class BasicFunctionalityTestCase(FlaskTestCase):
         self.assert_equal(rv['m'], flask.Markup('Hello!'))
         self.assert_equal(type(rv['m']), flask.Markup)
         self.assert_equal(rv['dt'], now)
+        self.assert_equal(rv['u'], the_uuid)
         self.assert_equal(rv['t'], (1, 2, 3))
 
     def test_flashes(self):