diff --git a/lib/response.js b/lib/response.js
index 39cdaef..5ef6708 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -4,10 +4,10 @@
  */
 
 var ensureErrorHandler = require('error-inject');
+var getType = require('mime-types').contentType;
 var isJSON = require('koa-is-json');
 var escape = require('escape-html');
 var onfinish = require('finished');
-var getType = require('set-type');
 var status = require('statuses');
 var destroy = require('dethroy');
 var http = require('http');
diff --git a/package.json b/package.json
index f7a826d..7d1991d 100644
--- a/package.json
+++ b/package.json
@@ -25,7 +25,7 @@
     "statuses": "~1.0.1",
     "accepts": "~1.0.0",
     "type-is": "~1.2.0",
-    "set-type": "~1.0.0",
+    "mime-types": "~1.0.0",
     "finished": "~1.1.1",
     "co": "~3.0.2",
     "debug": "*",
diff --git a/test/application.js b/test/application.js
index 8fbf9b8..5215d9a 100644
--- a/test/application.js
+++ b/test/application.js
@@ -177,7 +177,7 @@ describe('app.respond', function(){
       .expect(200)
       .end(function(err, res){
         if (err) return done(err);
-        res.should.have.header('Content-Type', 'application/json');
+        res.should.have.header('Content-Type', 'application/json; charset=utf-8');
         res.should.have.header('Content-Length', '17');
         assert(0 == res.text.length);
         done();
@@ -553,14 +553,14 @@ describe('app.respond', function(){
 
       app.use(function *(){
         this.body = fs.createReadStream('package.json');
-        this.set('Content-Type', 'application/json');
+        this.set('Content-Type', 'application/json; charset=utf-8');
       });
 
       var server = app.listen();
 
       request(server)
       .get('/')
-      .expect('Content-Type', 'application/json')
+      .expect('Content-Type', 'application/json; charset=utf-8')
       .end(function(err, res){
         if (err) return done(err);
         var pkg = require('../package');
@@ -576,14 +576,14 @@ describe('app.respond', function(){
       app.use(function *(){
         this.body = 'hello';
         this.body = fs.createReadStream('package.json');
-        this.set('Content-Type', 'application/json');
+        this.set('Content-Type', 'application/json; charset=utf-8');
       });
 
       var server = app.listen();
 
       request(server)
       .get('/')
-      .expect('Content-Type', 'application/json')
+      .expect('Content-Type', 'application/json; charset=utf-8')
       .end(function(err, res){
         if (err) return done(err);
         var pkg = require('../package');
@@ -599,14 +599,14 @@ describe('app.respond', function(){
       app.use(function *(){
         this.length = fs.readFileSync('package.json').length;
         this.body = fs.createReadStream('package.json');
-        this.set('Content-Type', 'application/json');
+        this.set('Content-Type', 'application/json; charset=utf-8');
       });
 
       var server = app.listen();
 
       request(server)
       .get('/')
-      .expect('Content-Type', 'application/json')
+      .expect('Content-Type', 'application/json; charset=utf-8')
       .end(function(err, res){
         if (err) return done(err);
         var pkg = require('../package');
@@ -624,14 +624,14 @@ describe('app.respond', function(){
         var stream = fs.createReadStream('package.json');
         this.body = stream;
         this.body = stream;
-        this.set('Content-Type', 'application/json');
+        this.set('Content-Type', 'application/json; charset=utf-8');
       });
 
       var server = app.listen();
 
       request(server)
       .get('/')
-      .expect('Content-Type', 'application/json')
+      .expect('Content-Type', 'application/json; charset=utf-8')
       .end(function(err, res){
         if (err) return done(err);
         var pkg = require('../package');
@@ -645,7 +645,7 @@ describe('app.respond', function(){
       var app = koa();
 
       app.use(function *(){
-        this.set('Content-Type', 'application/json');
+        this.set('Content-Type', 'application/json; charset=utf-8');
         this.body = fs.createReadStream('does not exist');
       });
 
@@ -703,7 +703,7 @@ describe('app.respond', function(){
 
       request(server)
       .get('/')
-      .expect('Content-Type', 'application/json')
+      .expect('Content-Type', 'application/json; charset=utf-8')
       .expect('{"hello":"world"}', done);
     })
   })
diff --git a/test/request/is.js b/test/request/is.js
index 415d9e5..9d83e3b 100644
--- a/test/request/is.js
+++ b/test/request/is.js
@@ -79,7 +79,7 @@ describe('ctx.is(type)', function(){
       ctx.is('jpeg').should.be.false;
       ctx.is('.jpeg').should.be.false;
       ctx.is('text/*', 'application/*').should.be.false;
-      ctx.is('text/html', 'text/plain', 'application/json').should.be.false;
+      ctx.is('text/html', 'text/plain', 'application/json; charset=utf-8').should.be.false;
     })
   })
 
diff --git a/test/response/body.js b/test/response/body.js
index 55358e0..a093436 100644
--- a/test/response/body.js
+++ b/test/response/body.js
@@ -20,7 +20,7 @@ describe('res.body=', function(){
         assert('text/html; charset=utf-8' == res.header['content-type']);
 
         res.body = { foo: 'bar' };
-        assert('application/json' == res.header['content-type']);
+        assert('application/json; charset=utf-8' == res.header['content-type']);
       })
     })
 
@@ -126,7 +126,7 @@ describe('res.body=', function(){
     it('should default to json', function(){
       var res = response();
       res.body = { foo: 'bar' };
-      assert('application/json' == res.header['content-type']);
+      assert('application/json; charset=utf-8' == res.header['content-type']);
     })
   })
 })
\ No newline at end of file
diff --git a/test/response/status.js b/test/response/status.js
index 2af64bf..f7f4bf8 100644
--- a/test/response/status.js
+++ b/test/response/status.js
@@ -42,7 +42,7 @@ describe('res.status=', function(){
 
       app.use(function *(){
         this.body = { foo: 'bar' };
-        this.set('Content-Type', 'application/json');
+        this.set('Content-Type', 'application/json; charset=utf-8');
         this.set('Content-Length', '15');
         this.set('Transfer-Encoding', 'chunked');
         this.status = status;
@@ -69,7 +69,7 @@ describe('res.status=', function(){
       app.use(function *(){
         this.status = status;
         this.body = { foo: 'bar' };
-        this.set('Content-Type', 'application/json');
+        this.set('Content-Type', 'application/json; charset=utf-8');
         this.set('Content-Length', '15');
         this.set('Transfer-Encoding', 'chunked');
       });
diff --git a/test/response/type.js b/test/response/type.js
index b5c8c48..1897d87 100644
--- a/test/response/type.js
+++ b/test/response/type.js
@@ -17,7 +17,7 @@ describe('ctx.type=', function(){
       var ctx = context();
       ctx.type = 'json';
       ctx.type.should.equal('application/json');
-      ctx.response.header['content-type'].should.equal('application/json');
+      ctx.response.header['content-type'].should.equal('application/json; charset=utf-8');
     })
   })
 
@@ -56,4 +56,4 @@ describe('ctx.type', function(){
       ctx.type.should.equal('application/json');
     })
   })
-})
\ No newline at end of file
+})