Bundler could not find compatible versions for gem "activemodel"

Trying to install mongoid 3.1.6 in rails 4.1

Bundler could not find compatible versions for gem "activemodel": In Gemfile:

mongoid (~> 3.1.6) ruby depends on
  activemodel (~> 3.2) ruby

rails (= 4.1.0) ruby depends on
  activerecord (= 4.1.0) ruby depends on
    activemodel (4.1.0)

It works fine when mongoid is downgraded to 1.0.6 but i need to use mongoid 3.1.6 in rails 4.1. Is there any solution to solve this problemt?

You'll need to use a 4.x version of mongoid, which uses activemodel >= 4.0.0. Here's the latest:

gem 'mongoid', '~> 4.0.0'