Active Record issue in Ruby on Rails

I'm trying to do db:migrate but I get this error:

DEPRECATION WARNING: require "activerecord" is deprecated and will be removed in Rails 3. Use require "active_r开发者_运维技巧ecord" instead. (called from /usr/lib/ruby/1.8/activerecord.rb:2)

What's the problem? I'm using Rails 3.0.9 with Ruby 1.8.7 & Ubuntu 11.04

---

Delete your Gemfile.lock and do bundle install once again.