diff --git a/paramiko/transport.py b/paramiko/transport.py
index 4f41a41..092ab1c 100644
--- a/paramiko/transport.py
+++ b/paramiko/transport.py
@@ -279,7 +279,6 @@ class Transport (threading.Thread):
 
         .. versionadded:: 1.5.3
         """
-        self.sock.close()
         self.close()
 
     def get_security_options(self):