PostgreSQL on Rails 3.2 not honoring sslmode

I have a Rails 3.2 app using an Amazon RDS PostgreSQL database. I want the app to connect to the database over SSL. My database.yml looks like this:

development:
  adapter: postgresql
  encoding: utf8
  database: xxx
  host: xxx.rds.amazonaws.com
  port: 1234
  sslmode: verify-full
  sslrootcert: <%= Rails.root %>/config/rds-combined-ca-bundle.pem
  username: xxx
  password: xxx

The sslrootcert is the public key downloaded from http://ift.tt/1CR7doI (see http://ift.tt/17AceqY)

The problem I am having is that sslmode verify-full does not seem to be working. I can change sslrootcert to /blah.pem and my database still connects and my Rails app functions. What am I missing?