rspec gets "undefined method `build_rb_world_factory' for nil"

I'm updating a Rails 3.2 app to Ruby 2.2.2. I've pulled the Rails version up to 3.2.22, which is necessary for Ruby 2.2.2. That went relatively well but prompted a Cucumber update, from 1.2.1 to 1.3.20. (I don't recall the details, because that was several failed efforts ago, but I think my features were passing but then exiting false before I did this.)

Now Cucumber features run fine (albeit with a ton of unrelated Ruby 2.2.2 warnings), but rspec does not. Specifically, when I run rake spec I get this error:

/path/to/gems/cucumber-1.3.20/lib/cucumber/rb_support/rb_dsl.rb:15:in `build_rb_world_factory': undefined method `build_rb_world_factory' for nil:NilClass (NoMethodError)

The stack trace leads through Capybara (2.4.4, pinned for other reasons), ActiveSupport, and Bundler back up to rspec-core.

All my searches trying to find similar issues just lead to the code, because it seems like the only place this method name exists is in code.

Why am I getting this error from Capybara/Cucumber when running rspec? How can I fix it?