diff --git a/lib/py/src/transport/TSocket.py b/lib/py/src/transport/TSocket.py
index 4645a02..5e58825 100644
--- a/lib/py/src/transport/TSocket.py
+++ b/lib/py/src/transport/TSocket.py
@@ -95,6 +95,8 @@
     return buff
 
   def write(self, buff):
+    if not self.handle:
+      raise TTransportException(TTransportException.NOT_OPEN, 'Transport not open')
     sent = 0
     have = len(buff)
     while sent < have: