diff --git a/lib/context.js b/lib/context.js
index 03b2d29..584f0e8 100644
--- a/lib/context.js
+++ b/lib/context.js
@@ -4,9 +4,6 @@
  */
 
 var debug = require('debug')('koa:context');
-var Request = require('./request');
-var Response = require('./response');
-var Cookies = require('cookies');
 var http = require('http');
 
 /**
diff --git a/lib/request.js b/lib/request.js
index 69ba291..f445ede 100644
--- a/lib/request.js
+++ b/lib/request.js
@@ -5,15 +5,9 @@
 
 var debug = require('debug')('koa:context');
 var Negotiator = require('negotiator');
-var statuses = require('./status');
 var qs = require('querystring');
-var Stream = require('stream');
 var fresh = require('fresh');
-var http = require('http');
-var path = require('path');
 var mime = require('mime');
-var basename = path.basename;
-var extname = path.extname;
 var url = require('url');
 var parse = url.parse;
 var stringify = url.format;
@@ -527,6 +521,7 @@ module.exports = {
     // ensure array
     if (!Array.isArray(types)) types = [].slice.call(arguments);
 
+    var mt;
     for (var i = 0; i < types.length; i++) {
       var type = types[i];
 
diff --git a/lib/response.js b/lib/response.js
index 30611a1..a3ea91b 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -4,20 +4,13 @@
  */
 
 var debug = require('debug')('koa:response');
-var Negotiator = require('negotiator');
 var statuses = require('./status');
-var Cookies = require('cookies');
-var qs = require('querystring');
 var Stream = require('stream');
-var fresh = require('fresh');
 var http = require('http');
 var path = require('path');
 var mime = require('mime');
 var basename = path.basename;
 var extname = path.extname;
-var url = require('url');
-var parse = url.parse;
-var stringify = url.format;
 
 /**
  * Prototype.