uninitialized constant Bundler (NameError) with rails 3

When I try to run some rspec test cases I'm getting this error

I'm using linux rails 3.0.0, ruby 1.9.2 (with RVM)

config/boot.rb:8: uninitialized constant Bundler (NameError)
from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
    from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `require' ..

But when do a gem list , it shows both builder (2.1.2) bundler (1.0.10)

so wha开发者_运维技巧t can be the problem?

Just update your bundler, in latest version such issue is resolved.

'gem install bundler'

and then 'bundler install'

If you find again error, then delete GEM.lock file, then run bundler install. It may resolve the issue.