diff --git a/portal/__init__.py b/portal/__init__.py
index f07b1e5..9e55272 100644
--- a/portal/__init__.py
+++ b/portal/__init__.py
@@ -1,4 +1,4 @@
-__version__ = '3.5.0'
+__version__ = '3.5.1'
 
 import multiprocessing as mp
 try:
diff --git a/portal/client_socket.py b/portal/client_socket.py
index 2187e06..1883b2b 100644
--- a/portal/client_socket.py
+++ b/portal/client_socket.py
@@ -238,9 +238,10 @@ def _create(self):
         sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, after)
         sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, every)
         sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, fails)
-        sock.setsockopt(
-            socket.IPPROTO_TCP, socket.TCP_USER_TIMEOUT,
-            1000 * (after + every * fails))
+        if hasattr(socket, 'TCP_USER_TIMEOUT'):  # Linux
+          sock.setsockopt(
+              socket.IPPROTO_TCP, socket.TCP_USER_TIMEOUT,
+              1000 * (after + every * fails))
       if sys.platform == 'darwin':
         sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
         sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPALIVE, every)