How to use Bundler with offline .gem file?

I’m using Rails 3.0.3, new to Rails 3 and bundler.

I got this same error with:

gem 'mygem', :path => '/path/to/gem'

Resolved by specifying the version number:

gem 'mygem', '0.0.1', :path => '/path/to/gem'

Using >=0.0.1 for the version reverted to the original error. I can’t explain any of this, however.

Quoting JD’s helpful commment, from the Gemfile man page: “Similar to the semantics of the :git option, the :path option requires that the directory in question either contains a .gemspec for the gem, or that you specify an explicit version that bundler should use.”