diff --git a/Rakefile b/Rakefile
index 000f8a3..75afd62 100644
--- a/Rakefile
+++ b/Rakefile
@@ -14,6 +14,7 @@ end
 task :default => :test
 
 Rake::RDocTask.new do |rdoc|
+  require File.expand_path('../lib/simple_oauth/version', __FILE__)
   version = SimpleOAuth::Version::STRING
   rdoc.rdoc_dir = 'rdoc'
   rdoc.title = "simple_oauth #{version}"
diff --git a/lib/simple_oauth.rb b/lib/simple_oauth.rb
index 0677a57..7c1303a 100644
--- a/lib/simple_oauth.rb
+++ b/lib/simple_oauth.rb
@@ -2,120 +2,4 @@ require 'base64'
 require 'cgi'
 require 'openssl'
 require 'uri'
-
-module SimpleOAuth
-  module Version
-    MAJOR = 0
-    MINOR = 1
-    PATCH = 2
-    STRING = [MAJOR, MINOR, PATCH].join('.')
-  end
-
-  class Header
-    ATTRIBUTE_KEYS = [:consumer_key, :nonce, :signature_method, :timestamp, :token, :version]
-
-    def self.default_options
-      {
-        :nonce => OpenSSL::Random.random_bytes(16).unpack('H*')[0],
-        :signature_method => 'HMAC-SHA1',
-        :timestamp => Time.now.to_i.to_s,
-        :version => '1.0'
-      }
-    end
-
-    def self.encode(value)
-      URI.encode(value.to_s, /[^a-z0-9\-\.\_\~]/i)
-    end
-
-    def self.decode(value)
-      URI.decode(value.to_s)
-    end
-
-    def self.parse(header)
-      header.to_s.sub(/^OAuth\s/, '').split(', ').inject({}) do |attributes, pair|
-        match = pair.match(/^(\w+)\=\"([^\"]*)\"$/)
-        attributes.merge(match[1].sub(/^oauth_/, '').to_sym => decode(match[2]))
-      end
-    end
-
-    attr_reader :method, :params, :options
-
-    def initialize(method, url, params, oauth = {})
-      @method = method.to_s.upcase
-      @uri = URI.parse(url).tap do |uri|
-        uri.scheme = uri.scheme.downcase
-        uri.normalize!
-        uri.fragment = nil
-      end
-      @params = params
-      @options = oauth.is_a?(Hash) ? self.class.default_options.merge(oauth) : self.class.parse(oauth)
-    end
-
-    def url
-      @uri.dup.tap{|u| u.query = nil }.to_s
-    end
-
-    def to_s
-      "OAuth #{normalized_attributes}"
-    end
-
-    def valid?(secrets = {})
-      original_options = options.dup
-      options.merge!(secrets)
-      valid = options[:signature] == signature
-      options.replace(original_options)
-      valid
-    end
-
-    def signed_attributes
-      attributes.merge(:oauth_signature => signature)
-    end
-
-    private
-      def normalized_attributes
-        signed_attributes.sort_by{|k,v| k.to_s }.map{|k,v| %(#{k}="#{self.class.encode(v)}") }.join(', ')
-      end
-
-      def attributes
-        ATTRIBUTE_KEYS.inject({}){|a,k| options.key?(k) ? a.merge(:"oauth_#{k}" => options[k]) : a }
-      end
-
-      def signature
-        send(options[:signature_method].downcase.tr('-', '_') + '_signature')
-      end
-
-      def hmac_sha1_signature
-        Base64.encode64(OpenSSL::HMAC.digest(OpenSSL::Digest::SHA1.new, secret, signature_base)).chomp.gsub(/\n/, '')
-      end
-
-      def secret
-        options.values_at(:consumer_secret, :token_secret).map{|v| self.class.encode(v) }.join('&')
-      end
-
-      def signature_base
-        [method, url, normalized_params].map{|v| self.class.encode(v) }.join('&')
-      end
-
-      def normalized_params
-        signature_params.map{|p| p.map{|v| self.class.encode(v) } }.sort.map{|p| p.join('=') }.join('&')
-      end
-
-      def signature_params
-        attributes.to_a + params.to_a + url_params
-      end
-
-      def url_params
-        CGI.parse(@uri.query || '').inject([]){|p,(k,vs)| p + vs.map{|v| [k, v] } }
-      end
-
-      def rsa_sha1_signature
-        Base64.encode64(private_key.sign(OpenSSL::Digest::SHA1.new, signature_base)).chomp.gsub(/\n/, '')
-      end
-
-      def private_key
-        OpenSSL::PKey::RSA.new(options[:consumer_secret])
-      end
-
-      alias_method :plaintext_signature, :secret
-  end
-end
+require File.expand_path('../simple_oauth/header', __FILE__)
diff --git a/lib/simple_oauth/header.rb b/lib/simple_oauth/header.rb
new file mode 100644
index 0000000..5d81a75
--- /dev/null
+++ b/lib/simple_oauth/header.rb
@@ -0,0 +1,110 @@
+module SimpleOAuth
+  class Header
+    ATTRIBUTE_KEYS = [:consumer_key, :nonce, :signature_method, :timestamp, :token, :version] unless defined? ::SimpleOAuth::Header::ATTRIBUTE_KEYS
+
+    def self.default_options
+      {
+        :nonce => OpenSSL::Random.random_bytes(16).unpack('H*')[0],
+        :signature_method => 'HMAC-SHA1',
+        :timestamp => Time.now.to_i.to_s,
+        :version => '1.0'
+      }
+    end
+
+    def self.encode(value)
+      URI.encode(value.to_s, /[^a-z0-9\-\.\_\~]/i)
+    end
+
+    def self.decode(value)
+      URI.decode(value.to_s)
+    end
+
+    def self.parse(header)
+      header.to_s.sub(/^OAuth\s/, '').split(', ').inject({}) do |attributes, pair|
+        match = pair.match(/^(\w+)\=\"([^\"]*)\"$/)
+        attributes.merge(match[1].sub(/^oauth_/, '').to_sym => decode(match[2]))
+      end
+    end
+
+    attr_reader :method, :params, :options
+
+    def initialize(method, url, params, oauth = {})
+      @method = method.to_s.upcase
+      @uri = URI.parse(url).tap do |uri|
+        uri.scheme = uri.scheme.downcase
+        uri.normalize!
+        uri.fragment = nil
+      end
+      @params = params
+      @options = oauth.is_a?(Hash) ? self.class.default_options.merge(oauth) : self.class.parse(oauth)
+    end
+
+    def url
+      @uri.dup.tap{|u| u.query = nil }.to_s
+    end
+
+    def to_s
+      "OAuth #{normalized_attributes}"
+    end
+
+    def valid?(secrets = {})
+      original_options = options.dup
+      options.merge!(secrets)
+      valid = options[:signature] == signature
+      options.replace(original_options)
+      valid
+    end
+
+    def signed_attributes
+      attributes.merge(:oauth_signature => signature)
+    end
+
+    private
+
+    def normalized_attributes
+      signed_attributes.sort_by{|k,v| k.to_s }.map{|k,v| %(#{k}="#{self.class.encode(v)}") }.join(', ')
+    end
+
+    def attributes
+      ATTRIBUTE_KEYS.inject({}){|a,k| options.key?(k) ? a.merge(:"oauth_#{k}" => options[k]) : a }
+    end
+
+    def signature
+      send(options[:signature_method].downcase.tr('-', '_') + '_signature')
+    end
+
+    def hmac_sha1_signature
+      Base64.encode64(OpenSSL::HMAC.digest(OpenSSL::Digest::SHA1.new, secret, signature_base)).chomp.gsub(/\n/, '')
+    end
+
+    def secret
+      options.values_at(:consumer_secret, :token_secret).map{|v| self.class.encode(v) }.join('&')
+    end
+    alias_method :plaintext_signature, :secret
+
+    def signature_base
+      [method, url, normalized_params].map{|v| self.class.encode(v) }.join('&')
+    end
+
+    def normalized_params
+      signature_params.map{|p| p.map{|v| self.class.encode(v) } }.sort.map{|p| p.join('=') }.join('&')
+    end
+
+    def signature_params
+      attributes.to_a + params.to_a + url_params
+    end
+
+    def url_params
+      CGI.parse(@uri.query || '').inject([]){|p,(k,vs)| p + vs.map{|v| [k, v] } }
+    end
+
+    def rsa_sha1_signature
+      Base64.encode64(private_key.sign(OpenSSL::Digest::SHA1.new, signature_base)).chomp.gsub(/\n/, '')
+    end
+
+    def private_key
+      OpenSSL::PKey::RSA.new(options[:consumer_secret])
+    end
+
+  end
+end
diff --git a/lib/simple_oauth/version.rb b/lib/simple_oauth/version.rb
new file mode 100644
index 0000000..2c45aa7
--- /dev/null
+++ b/lib/simple_oauth/version.rb
@@ -0,0 +1,8 @@
+module SimpleOAuth
+  module Version
+    MAJOR = 0 unless defined? ::SimpleOAuth::Version::MAJOR
+    MINOR = 1 unless defined? ::SimpleOAuth::Version::MINOR
+    PATCH = 2 unless defined? ::SimpleOAuth::Version::PATCH
+    STRING = [MAJOR, MINOR, PATCH].join('.') unless defined? ::SimpleOAuth::Version::STRING
+  end
+end
diff --git a/simple_oauth.gemspec b/simple_oauth.gemspec
index c1baaa3..a526da9 100644
--- a/simple_oauth.gemspec
+++ b/simple_oauth.gemspec
@@ -1,5 +1,5 @@
 # -*- encoding: utf-8 -*-
-require File.expand_path('../lib/simple_oauth', __FILE__)
+require File.expand_path('../lib/simple_oauth/version', __FILE__)
 
 Gem::Specification.new do |spec|
   spec.add_development_dependency('mocha', '>= 0')