diff --git a/eventlet/hubs/poll.py b/eventlet/hubs/poll.py
index ab214f4..b1f4b6e 100644
--- a/eventlet/hubs/poll.py
+++ b/eventlet/hubs/poll.py
@@ -23,8 +23,7 @@ class Hub(BaseHub):
             self.modify = self.poll.register
 
     def add(self, evtype, fileno, cb):
-        oldlisteners = bool(self.listeners[READ].get(fileno) or
-                            self.listeners[WRITE].get(fileno))
+        oldlisteners = bool(self.listeners[evtype].get(fileno))
         listener = super(Hub, self).add(evtype, fileno, cb)
         if not oldlisteners:
             # Means we've added a new listener