diff --git a/cassandra/pool.py b/cassandra/pool.py
index d6b4b87e..a810d603 100644
--- a/cassandra/pool.py
+++ b/cassandra/pool.py
@@ -282,6 +282,7 @@ class HostConnection(object):
         self.host_distance = host_distance
         self._session = weakref.proxy(session)
         self._lock = Lock()
+        self._is_replacing = False
 
         if host_distance == HostDistance.IGNORED:
             log.debug("Not opening connection to ignored host %s", self.host)