diff --git a/sjrpc/core/async.py b/sjrpc/core/async.py
index 894bd100794c940ffb1ae508702dd3c0bd28f0eb..f7130a86f97e2e63d0d741fb7e54d053bdf8d483 100644
--- a/sjrpc/core/async.py
+++ b/sjrpc/core/async.py
@@ -68,13 +68,13 @@ class AsyncWatcher(object):
            >>>     process(msg)
         '''
         responses = []
-        time_remains = timeout
         while self._expected_responses:
             try:
-                dt, response = self._get_in_queue(timeout=time_remains)
+                dt, response = self._get_in_queue(timeout=timeout)
             except Empty:
                 break
-            time_remains -= dt
+            if timeout is not None:
+                timeout -= dt
             responses.append(response)
             self._expected_responses.remove(response['id'])
             # Check for max_wait: