diff --git a/cassandra/cluster.py b/cassandra/cluster.py
index e59fbb27..2552328b 100644
--- a/cassandra/cluster.py
+++ b/cassandra/cluster.py
@@ -785,7 +785,6 @@ class Cluster(object):
                 self.control_connection.wait_for_schema_agreement(connection)
             except Exception:
                 log.debug("Error waiting for schema agreement before preparing statements against host %s", host, exc_info=True)
-                # TODO: potentially error out the connection?
 
             statements = self._prepared_statements.values()
             for keyspace, ks_statements in groupby(statements, lambda s: s.keyspace):
diff --git a/cassandra/io/asyncorereactor.py b/cassandra/io/asyncorereactor.py
index 74373576..60c4078e 100644
--- a/cassandra/io/asyncorereactor.py
+++ b/cassandra/io/asyncorereactor.py
@@ -370,7 +370,13 @@ class AsyncoreConnection(Connection, asyncore.dispatcher):
                         raise OperationTimedOut()
                 time.sleep(0.01)
 
-        return waiter.deliver(timeout)
+        try:
+            return waiter.deliver(timeout)
+        except OperationTimedOut:
+            raise
+        except Exception, exc:
+            self.defunct(exc)
+            raise
 
     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 10475d1f..4cbc676d 100644
--- a/cassandra/io/libevreactor.py
+++ b/cassandra/io/libevreactor.py
@@ -418,7 +418,13 @@ class LibevConnection(Connection):
                         raise OperationTimedOut()
                 time.sleep(0.01)
 
-        return waiter.deliver(timeout)
+        try:
+            return waiter.deliver(timeout)
+        except OperationTimedOut:
+            raise
+        except Exception, exc:
+            self.defunct(exc)
+            raise
 
     def register_watcher(self, event_type, callback):
         self._push_watchers[event_type].add(callback)