diff --git a/tornado/test/twisted_test.py b/tornado/test/twisted_test.py
index b8d9c6f7..003b539d 100644
--- a/tornado/test/twisted_test.py
+++ b/tornado/test/twisted_test.py
@@ -478,6 +478,10 @@ if have_twisted:
             "test_lostFileDescriptor",  # incompatible with epoll and kqueue
         ],
         'twisted.internet.test.test_process.ProcessTestsBuilder': [
+            # Only work as root.  Twisted's "skip" functionality works
+            # with py27+, but not unittest2 on py26.
+            'test_changeGID',
+            'test_changeUID',
         ],
         # Process tests appear to work on OSX 10.7, but not 10.6
         #'twisted.internet.test.test_process.PTYProcessTestsBuilder': [
diff --git a/tox.ini b/tox.ini
index 3d143c3a..54b2f7ac 100644
--- a/tox.ini
+++ b/tox.ini
@@ -28,15 +28,13 @@ changedir = {toxworkdir}
 basepython = python2.6
 deps = unittest2
 
-# py26-full deliberately runs an older version of twisted to ensure
-# we're still compatible with the oldest version we support.
 [testenv:py26-full]
 basepython = python2.6
 deps =
      futures
      mock
      pycurl
-     twisted==11.0.0
+     twisted>=11.0.0
      unittest2
 
 [testenv:py27-full]
@@ -45,7 +43,7 @@ deps =
      futures
      mock
      pycurl
-     twisted>=12.2.0
+     twisted>=11.0.0
 
 [testenv:py27-curl]
 # Same as py27-full, but runs the tests with curl_httpclient by default.
@@ -56,7 +54,7 @@ deps =
      futures
      mock
      pycurl
-     twisted>=11.1.0
+     twisted>=11.0.0
 commands = python -m tornado.test.runtests --httpclient=tornado.curl_httpclient.CurlAsyncHTTPClient {posargs:}
 
 [testenv:py27-select]
@@ -68,7 +66,7 @@ deps =
      futures
      mock
      pycurl
-     twisted>=12.0.0
+     twisted>=11.0.0
 commands = python -m tornado.test.runtests --ioloop=tornado.platform.select.SelectIOLoop {posargs:}
 
 [testenv:py26-twisted]