Bundler could not find compatible versions for gem "activesupport"

Question

I migrated to 3.2.13 version of rails and I am getting this error, how do I get rid of this?

Fetching gem metadata from https://rubygems.org/.......
Fetching gem metadata from https://rubygems.org/..
Resolving dependencies...
Bundler could not find compatible versions for gem "activesupport":
  In snapshot (Gemfile.lock):
    activesupport (3.2.12)

  In Gemfile:
    rails (= 3.2.13) ruby depends on
      activesupport (= 3.2.13) ruby

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.

EDIT

sinatra (1.3.6)
  rack (~> 1.4)
  rack-protection (~> 1.3)
  tilt (~> 1.3, >= 1.3.3)

Answer 1

For anyone who accidently comes to this link (at the time google served this page first); check out this post Bundler could not find compatible versions for gem, updating Rails app

My steps were run

gem update rails

rm Gemfile.lock

change my Gemfile to reference the version of rails i wanted

gem 'rails', '3.2.13'

finally run

bundle install 

I didn't try bundle update as @PistachioPony suggested but that might take the place of removing the lock file and rebuilding.