diff --git a/README.rdoc b/README.rdoc
index 9a4c1ee..c07ce85 100644
--- a/README.rdoc
+++ b/README.rdoc
@@ -1,10 +1,11 @@
 == foursquare APIv2 Sinatra Example
 
-This shows how easy it is to use Foursquare APIv2 via the OAuth2 gem.
+This shows how easy it is to use Foursquare APIv2 via the OAuth2 gem (requires v0.4.1).
 
 == code
     require 'rubygems'
     require 'sinatra'
+    gem 'oauth2', '=0.4.1'
     require 'oauth2'
     require 'json'
     require 'net/https'
@@ -53,4 +54,4 @@ This shows how easy it is to use Foursquare APIv2 via the OAuth2 gem.
 
     get '/' do
       redirect client.web_server.authorize_url(:redirect_uri => redirect_uri)
-    end
\ No newline at end of file
+    end