diff --git a/paramiko/client.py b/paramiko/client.py
index c5a2d1a..4adcfe7 100644
--- a/paramiko/client.py
+++ b/paramiko/client.py
@@ -189,8 +189,8 @@ class SSHClient (object):
 
         # update local host keys from file (in case other SSH clients
         # have written to the known_hosts file meanwhile.
-        if self.known_hosts is not None:
-            self.load_host_keys(self.known_hosts)
+        if self._host_keys_filename is not None:
+            self.load_host_keys(self._known_keys_filename)
 
         f = open(filename, 'w')
         for hostname, keys in self._host_keys.iteritems():