diff --git a/sjrpc/core/rpcconnection.py b/sjrpc/core/rpcconnection.py
index 62435fd0e8c171e29259d87ed4133dc14b8b996e..be7515667fa3524206969f3c6f418feb6f0455f2 100644
--- a/sjrpc/core/rpcconnection.py
+++ b/sjrpc/core/rpcconnection.py
@@ -103,8 +103,9 @@ class RpcConnection(object):
             sent = self._sock.send(data)
             data = data[sent:]
 
-        if not len(self._outbound_buffer):
-            self._manager.nothing_to_write(self)
+        with self._outbound_buffer:
+            if not len(self._outbound_buffer):
+                self._manager.nothing_to_write(self)
     
     def receive(self):
         '''
@@ -143,8 +144,9 @@ class RpcConnection(object):
         logging.debug('Sending: %s' % message)
         json_msg = json.dumps(message)
         size = struct.pack('!L', len(json_msg))
-        self._outbound_buffer.push(size + json_msg)
-        self._manager.data_to_write(self)
+        with self._outbound_buffer:
+            self._outbound_buffer.push(size + json_msg)
+            self._manager.data_to_write(self)
     
     def _send_call(self, method_name, *args, **kwargs):
         '''