If you’ve tried out Rails 3 on Ruby 1.9.1 (like myself) you might of noticed that a lot of errors are being sent to stderr, it’ll look something like this:
Ozawa Sakuro has posted a fix for this on GitHub. You can see the original thread here, or simply follow the directions below to quickly fix it without trolling through the entire discussion:
1. Edit lib/bundler.rb:
4: require 'bundler/rubygems-ext' # originally 'bundler/rubygems'
2. Next rename lib/bundler/rubygems.rb to rubygems-ext.rb and then edit the file and wrap the require in a control structure as shown below:
1: unless defined? Gem 2: require 'rubygems' 3: require 'rubygems/specification' 4: end
I’ve tested this fix and it works with Bundler 0.9.3. Version 0.9.4 resolves the issue (thanks for the update Christian). In any event I hope this little nugget of information helps reduce the hair pulling.


Thank you for this summary. I left a comment about it in Railscasts#200, maybe Ryan will spread it out
The bugfix release of bundler was just released … so do an update gem and get bundler 0.9.4 which solves the error