just a warning but why 'server name not matching' ?

[kadoudal]

I bought and installed easily a certificate for my domain : mydomain.com (valid also for www.mydomain.com...)
and my SSL access are running well... (https://www.mydomain.com/..)

but I can see in the access.log the following warning :

[warn] RSA server certificate CommonName (CN) `www.mydomain.com' does NOT match server name!?
what did I miss in the Plesk console to suppress this message ?

thanks for your suggestions

erwin