diff --git a/lib/oauth2/error.rb b/lib/oauth2/error.rb
index a5d3f70a..c49a5535 100644
--- a/lib/oauth2/error.rb
+++ b/lib/oauth2/error.rb
@@ -1,5 +1,3 @@
-require 'kconv'
-
 module OAuth2
   class Error < StandardError
     attr_reader :response, :code, :description
@@ -10,25 +8,33 @@ def initialize(response)
       response.error = self
       @response = response
 
-      message = []
-
       if response.parsed.is_a?(Hash)
         @code = response.parsed['error']
         @description = response.parsed['error_description']
-        message << "#{@code}: #{@description}"
+        error_description = "#{@code}: #{@description}"
       end
 
-      if message[0] && message[0].respond_to?(:encoding)
-        script_encoding = message[0].encoding
-        response_body_encoding = response.body.encoding
-        response_body = response.body.kconv(script_encoding, response_body_encoding)
-      else
-        response_body = response.body
-      end
+      super(error_message(response.body, :error_description => error_description))
+    end
+
+    # Makes a error message
+    # @param [String] response_body response body of request
+    # @param [String] opts :error_description error description to show first line
+    def error_message(response_body, opts = {})
+      message = []
+
+      opts[:error_description] && message << opts[:error_description]
+
+      error_message = if opts[:error_description] && opts[:error_description].respond_to?(:encoding)
+                        script_encoding = opts[:error_description].encoding
+                        response_body.encode(script_encoding)
+                      else
+                        response_body
+                      end
 
-      message << response_body
+      message << error_message
 
-      super(message.join("\n"))
+      message.join("\n")
     end
   end
 end
diff --git a/spec/oauth2/client_spec.rb b/spec/oauth2/client_spec.rb
index 26d65c87..ef65f085 100644
--- a/spec/oauth2/client_spec.rb
+++ b/spec/oauth2/client_spec.rb
@@ -1,6 +1,6 @@
 # coding: utf-8
 require 'helper'
-require 'kconv'
+require 'nkf'
 
 describe OAuth2::Client do
   let!(:error_value) { 'invalid_token' }
@@ -18,7 +18,7 @@
         stub.post('/redirect')          { |env| [303, {'Content-Type' => 'text/plain', 'location' => '/reflect'}, ''] }
         stub.get('/error')              { |env| [500, {'Content-Type' => 'text/plain'}, 'unknown error'] }
         stub.get('/empty_get')          { |env| [204, {}, nil] }
-        stub.get('/different_encoding') { |env| [500, {'Content-Type' => 'application/json'}, MultiJson.encode(:error => error_value, :error_description => "∞").kconv(Kconv::EUC, Kconv::UTF8)] }
+        stub.get('/different_encoding') { |env| [500, {'Content-Type' => 'application/json'}, NKF.nkf('-We', MultiJson.encode(:error => error_value, :error_description => "∞"))] }
       end
     end
   end