Amazon RDS / EC2: Allow a connection from two ips only (Home and EC2 machine)

I'm trying to get a connection to work from my server (EC2) to RDS. I've setup two inbound rules, one for my home ip, and another for my EC2 ip. PHP on the server fails to connect. If I change one of the rules to allow from any ip, PHP connects successfully...

How should I setup my rules to be able to connect directly to the RDS db from my desktop, and to grant access only to my EC2 server?