Install Gems from Vendor Cache

I'm using Bundler with Capistrano to deploy my application. In spite of
the fact Capistrano executes bundle install with the flag '--local',
gems from the vendor cache are NOT installed into the shared bundle
path. Instead I'm notified that:

    Some gems seem to be missing from your vendor/cache directory.

    Could not find libv8- in any of the sources

libv8- is definitely located in the vendor cache. Does anyone
know why bundler won't install the gems from the cache?

The full (bundler) command Capistrano executes is below.

cd /home/ari/apps/air/releases/20120209214139 && bundle install
--gemfile /home/ari/apps/air/releases/20120209214139/Gemfile --path
/home/ari/apps/air/shared/bundle --deployment --local --quiet --without
development test