HAProxy use server when comes from DOWN to UP

I have a server that runs HAProxy to load balance our mysql servers. Some of the server may go down when we have low average load for a extensive period of time, but, in the future, if the load becomes high again, those servers goes up automatically. The problem is when an instance goes down, HAProxy never looks to it again, so when the instance is up again, it is ignored. To fix this we reboot when needed.

Here is our configuration file:

global
    log 127.0.0.1 local0 notice
    user haproxy
    group haproxy

defaults
    log global
    retries 2
    timeout connect 3000
    timeout server 5000
    timeout client 5000

listen mysql-cluster
        bind 0.0.0.0:3306
        mode tcp
        option mysql-check user haproxy_check
        balance leastconn
        server mysql-1 ********:3306 check
        server mysql-2 ********:3306 check

Maybe if I change the retries from 2 to a big number it could solve our problem?

EDIT As requested, here is my HAProxy version:

$ haproxy -v
HA-Proxy version 1.4.24 2013/06/17
Copyright 2000-2013 Willy Tarreau <w@1wt.eu>

Thanks