diff --git a/daphne/server.py b/daphne/server.py
index 6a65ebb..d8d43f2 100755
--- a/daphne/server.py
+++ b/daphne/server.py
@@ -195,6 +195,10 @@ class Server(object):
         """
         Coroutine that jumps the reply message from asyncio to Twisted
         """
+        # Don't do anything if the connection is closed
+        if self.connections[protocol].get("disconnected", None):
+            return
+        # Let the protocol handle it
         protocol.handle_reply(message)
 
     ### Utility
diff --git a/setup.cfg b/setup.cfg
index 4223ddf..8c9a5f5 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -7,6 +7,7 @@ addopts = tests/
 [isort]
 line_length = 120
 multi_line_output = 3
+known_first_party = channels,daphne,asgiref
 
 [flake8]
 exclude = venv/*,tox/*,docs/*,testproject/*,js_client/*,.eggs/*