Unexpected "certificate verify failed" which does not match MRI behavior

You can reproduce this issue with the following code:

require 'open-uri'
open("https://medioh-studio.s3.amazonaws.com/").read

On MRI (1.8.7) I get this:

OpenURI::HTTPError: 403 Forbidden

Which is the expected error in this case. The SSL certificate is verified and the anticipated response code is returned from Amazon's servers.

On JRuby 1.5.1 I get this:

OpenSSL::SSL::SSLError: certificate verify failed

This error seems to occur regardless of what version of jruby-openssl is installed. Perhaps open-uri is doing some custom stuff here which is breaking?