How to run ferret (act_as_ferret) with jruby?

I have an existing project that uses the stone "act_as_ferret".

I installed it (and other necessary gems) and tried to run the db-migration script.

I get the following error:

gems/rails-2.3.4/lib/rails/gem_dependency.rb:119:Warning: Gem::Dependency#version_requirements is deprecated and will be removed on or after August 2010.  Use #requirement
no such file to load -- ferret

and in the end:

script/server:4
Missing these required gems:
  acts_as_ferret  = 0.4.4

when I list my gems it acts like a ferret. I suppose this is due to a choret that I cannot install because I use jruby. (I get my own extension error)

How to solve this problem? Thank.