diff --git a/docs/changelog.rst b/docs/changelog.rst
index 7f9b23a5..ea52ef29 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -176,7 +176,8 @@ Thanks!
 
 Mitogen would not be possible without the support of users. A huge thanks for
 bug reports, testing, features and fixes in this release contributed by
-`Fabian Arrotin <https://github.com/arrfab>`_, and
+`Fabian Arrotin <https://github.com/arrfab>`_,
+`Percy Grunwald <https://github.com/percygrunwald>`_,
 `Petr Enkov <https://github.com/enkov>`_, and
 `@elbunda <https://github.com/elbunda>`_.
 
diff --git a/mitogen/core.py b/mitogen/core.py
index 607c4bfb..578337f7 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -140,7 +140,6 @@ try:
 except NameError:
     BaseException = Exception
 
-IS_WSL = 'Microsoft' in os.uname()[2]
 PY24 = sys.version_info < (2, 5)
 PY3 = sys.version_info > (3,)
 if PY3:
@@ -164,6 +163,14 @@ try:
 except NameError:
     next = lambda it: it.next()
 
+# #550: prehistoric WSL did not advertise itself in uname output.
+try:
+    fp = open('/proc/sys/kernel/osrelease')
+    IS_WSL = 'Microsoft' in fp.read()
+    fp.close()
+except IOError:
+    IS_WSL = False
+
 
 #: Default size for calls to :meth:`Side.read` or :meth:`Side.write`, and the
 #: size of buffers configured by :func:`mitogen.parent.create_socketpair`. This
diff --git a/mitogen/parent.py b/mitogen/parent.py
index f25bd6c2..3d02bc43 100644
--- a/mitogen/parent.py
+++ b/mitogen/parent.py
@@ -371,11 +371,12 @@ def create_child(args, merge_stdio=False, stderr_pipe=False, preexec_fn=None):
 
 def _acquire_controlling_tty():
     os.setsid()
-    if sys.platform == 'linux2':
+    if sys.platform in ('linux', 'linux2'):
         # On Linux, the controlling tty becomes the first tty opened by a
         # process lacking any prior tty.
         os.close(os.open(os.ttyname(2), os.O_RDWR))
-    if hasattr(termios, 'TIOCSCTTY'):
+    if hasattr(termios, 'TIOCSCTTY') and not mitogen.core.IS_WSL:
+        # #550: prehistoric WSL does not like TIOCSCTTY.
         # On BSD an explicit ioctl is required. For some inexplicable reason,
         # Python 2.6 on Travis also requires it.
         fcntl.ioctl(2, termios.TIOCSCTTY)
diff --git a/mitogen/service.py b/mitogen/service.py
index dc200b95..302e81ab 100644
--- a/mitogen/service.py
+++ b/mitogen/service.py
@@ -451,7 +451,7 @@ class Pool(object):
     """
     activator_class = Activator
 
-    def __init__(self, router, services, size=1, overwrite=False):
+    def __init__(self, router, services=(), size=1, overwrite=False):
         self.router = router
         self._activator = self.activator_class()
         self._ipc_latch = mitogen.core.Latch()