Mysql2 gem installed but can't be required

I'm converting a Rails-2.3 project over to 3.0.3, and I'm running into a vexing issue with the mysql2 gem. It's listed in my Gemfile, I ran bundle install successfully. When I list my local gems, mysql2 is there.

But when I try to open a rails console I get this stacktrace that tells me mysql2 isn't installe开发者_高级运维d.

I'm using RVM for gem management as you can tell from the stacktrace, but everything else in the environment seems to be working okay.

I had forgotten to change the adapter in database.yml:

development:
  adapter: mysql2