Has the default behaviour of trying ssh-agent keys changed?

At some time in the past whenever I tried an ssh connection to a server without specifying the password ssh would try all the keys in ssh-agent to the point where if there were too many keys, my IP address could be barred for too many connection failures. The behaviour seems to have changed in that even if there is a single valid key in the ssh-agent list I have to include it in the command, eg ssh -i ~/.ssh/alternate-key user@host. Is this due to some change configuration setting or a change in the behaviour of the ssh executable itself.