In Bundler, how can I override a dependency's version requirements for its own dependencies?

I have a couple of needs in my application for which working on edge Rails (3.1) would help me complete my task faster.

The problem is that one of the gems I depend on doesn't yet officially support Rails 3.1, and it has a "~> 3.0.0" railties dependency, which creates a dependency conflict and bundler can't resolve my dependencies. Can I override that 开发者_如何学编程requirement in my app's Gemfile somehow, or is my only workaround to fork my dependency?

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Sadly, branching it is the only way to unravel that. Or, being more hacky, modifying the /vendor local installation of the gem.