diff --git a/contrib/TorControl.py b/contrib/TorControl.py
index 9c1aba89c5..0c1609aca8 100755
--- a/contrib/TorControl.py
+++ b/contrib/TorControl.py
@@ -210,7 +210,7 @@ def _receive_msg(s):
   length,type = struct.unpack("!HH",header)
   if length:
     while length > len(body):
-      body += s.recv(length)
+      body += s.recv(length-len(body))
   return length,type,body
 
 def receive_message(s):