diff --git a/cassandra/connection.py b/cassandra/connection.py
index 027259ea..22d4fd01 100644
--- a/cassandra/connection.py
+++ b/cassandra/connection.py
@@ -357,13 +357,16 @@ class Connection(object):
 
 class ResponseWaiter(object):
 
-    def __init__(self, num_responses):
+    def __init__(self, connection, num_responses):
+        self.connection = connection
         self.pending = num_responses
         self.error = None
         self.responses = [None] * num_responses
         self.event = Event()
 
     def got_response(self, response, index):
+        with self.connection.lock:
+            self.connection.in_flight -= 1
         if isinstance(response, Exception):
             self.error = response
             self.event.set()
diff --git a/cassandra/io/asyncorereactor.py b/cassandra/io/asyncorereactor.py
index 706e7b7c..74373576 100644
--- a/cassandra/io/asyncorereactor.py
+++ b/cassandra/io/asyncorereactor.py
@@ -347,7 +347,7 @@ class AsyncoreConnection(Connection, asyncore.dispatcher):
 
     def wait_for_responses(self, *msgs, **kwargs):
         timeout = kwargs.get('timeout')
-        waiter = ResponseWaiter(len(msgs))
+        waiter = ResponseWaiter(self, len(msgs))
 
         # busy wait for sufficient space on the connection
         messages_sent = 0
@@ -370,11 +370,7 @@ class AsyncoreConnection(Connection, asyncore.dispatcher):
                         raise OperationTimedOut()
                 time.sleep(0.01)
 
-        try:
-            return waiter.deliver(timeout)
-        finally:
-            with self.lock:
-                self.in_flight -= len(msgs)
+        return waiter.deliver(timeout)
 
     def register_watcher(self, event_type, callback):
         self._push_watchers[event_type].add(callback)
diff --git a/cassandra/io/libevreactor.py b/cassandra/io/libevreactor.py
index e5dbcd7b..10475d1f 100644
--- a/cassandra/io/libevreactor.py
+++ b/cassandra/io/libevreactor.py
@@ -395,7 +395,7 @@ class LibevConnection(Connection):
 
     def wait_for_responses(self, *msgs, **kwargs):
         timeout = kwargs.get('timeout')
-        waiter = ResponseWaiter(len(msgs))
+        waiter = ResponseWaiter(self, len(msgs))
 
         # busy wait for sufficient space on the connection
         messages_sent = 0
@@ -418,11 +418,7 @@ class LibevConnection(Connection):
                         raise OperationTimedOut()
                 time.sleep(0.01)
 
-        try:
-            return waiter.deliver(timeout)
-        finally:
-            with self.lock:
-                self.in_flight -= len(msgs)
+        return waiter.deliver(timeout)
 
     def register_watcher(self, event_type, callback):
         self._push_watchers[event_type].add(callback)