BUNDLER_WARNING : <<EOS Looks like your app's ./bin/rails is a stub that was generated by Bundler. In Rails 4, your app's bin/ directory contains executables that are versioned like any other source code, rather than stubs that are generated on demand. Here's how to upgrade: bundle config --delete bin # Turn off Bundler's stub generator rake rails:update:bin # Use the new Rails 4 executables git add bin # Add bin/ to source control You may need to remove bin/ from your .gitignore as well. When you install a gem whose executable you want to use in your app, generate it and add it to source control: bundle binstubs some-gem-name git add bin/new-executable EOS