diff --git a/tornado/iostream.py b/tornado/iostream.py
index 0ec3bd6f83..18b4460acd 100644
--- a/tornado/iostream.py
+++ b/tornado/iostream.py
@@ -43,6 +43,11 @@
 except ImportError:
     ssl = None
 
+try:
+    from tornado.platform.posix import _set_nonblocking
+except ImportError:
+    _set_nonblocking = None
+
 
 class BaseIOStream(object):
     """A utility class to write to and read from a non-blocking file or socket.
@@ -804,7 +809,6 @@ class PipeIOStream(BaseIOStream):
     by `os.pipe`) rather than an open file object.
     """
     def __init__(self, fd, *args, **kwargs):
-        from tornado.platform.posix import _set_nonblocking
         self.fd = fd
         _set_nonblocking(fd)
         super(PipeIOStream, self).__init__(*args, **kwargs)
diff --git a/tornado/test/iostream_test.py b/tornado/test/iostream_test.py
index 9f5b5cf09c..119a4f6cd8 100644
--- a/tornado/test/iostream_test.py
+++ b/tornado/test/iostream_test.py
@@ -4,7 +4,7 @@
 from tornado.iostream import IOStream, SSLIOStream, PipeIOStream
 from tornado.log import gen_log
 from tornado.testing import AsyncHTTPTestCase, AsyncHTTPSTestCase, AsyncTestCase, bind_unused_port, ExpectLog
-from tornado.test.util import unittest
+from tornado.test.util import unittest, skipIfNonUnix
 from tornado.util import b
 from tornado.web import RequestHandler, Application
 import errno
@@ -415,3 +415,4 @@ def test_pipe_iostream(self):
         self.assertEqual(data, b("ld"))
 
         rs.close()
+TestPipeIOStream = skipIfNonUnix(TestPipeIOStream)
diff --git a/tornado/test/process_test.py b/tornado/test/process_test.py
index 950aa8d454..7bd7503407 100644
--- a/tornado/test/process_test.py
+++ b/tornado/test/process_test.py
@@ -14,7 +14,7 @@
 from tornado.process import fork_processes, task_id, Subprocess
 from tornado.simple_httpclient import SimpleAsyncHTTPClient
 from tornado.testing import bind_unused_port, ExpectLog, AsyncTestCase
-from tornado.test.util import unittest
+from tornado.test.util import unittest, skipIfNonUnix
 from tornado.util import b
 from tornado.web import RequestHandler, Application
 
@@ -120,8 +120,7 @@ def fetch(url, fail_ok=False):
             except Exception:
                 logging.error("exception in child process %d", id, exc_info=True)
                 raise
-ProcessTest = unittest.skipIf(os.name != 'posix' or sys.platform == 'cygwin',
-                              "non-unix platform")(ProcessTest)
+ProcessTest = skipIfNonUnix(ProcessTest)
 
 
 class SubprocessTest(AsyncTestCase):
@@ -167,3 +166,4 @@ def test_sigchild_signal(self):
         self.assertEqual(subproc.returncode, ret)
         self.assertTrue(os.WIFSIGNALED(ret))
         self.assertEqual(os.WTERMSIG(ret), signal.SIGTERM)
+SubprocessTest = skipIfNonUnix(SubprocessTest)
diff --git a/tornado/test/util.py b/tornado/test/util.py
index 26d843d5bf..b048b5027f 100644
--- a/tornado/test/util.py
+++ b/tornado/test/util.py
@@ -1,5 +1,6 @@
 from __future__ import absolute_import, division, with_statement
 
+import os
 import sys
 
 # Encapsulate the choice of unittest or unittest2 here.
@@ -8,3 +9,6 @@
     import unittest
 else:
     import unittest2 as unittest
+
+skipIfNonUnix = unittest.skipIf(os.name != 'posix' or sys.platform == 'cygwin',
+                                "non-unix platform")