diff --git a/lib/response.js b/lib/response.js
index c3df5e9..1415d07 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -243,7 +243,7 @@ module.exports = {
 
   /**
    * Set Content-Type response header with `type` through `mime.lookup()`
-   * when it does not contain "/", or set the Content-Type to `type` otherwise.
+   * when it does not contain a charset.
    *
    * Examples:
    *
@@ -258,8 +258,11 @@ module.exports = {
    */
 
   set type(type) {
-    if (!~type.indexOf('/')) {
-      type = mime.lookup(type);
+    // mime
+    if (!~type.indexOf('/')) type = mime.lookup(type);
+
+    // charset
+    if (!~type.indexOf('charset')) {
       var cs = mime.charsets.lookup(type);
       if (cs) type += '; charset=' + cs.toLowerCase();
     }
diff --git a/test/response/type.js b/test/response/type.js
index 2fbceb5..b5c8c48 100644
--- a/test/response/type.js
+++ b/test/response/type.js
@@ -8,7 +8,7 @@ describe('ctx.type=', function(){
       var ctx = context();
       ctx.type = 'text/plain';
       ctx.type.should.equal('text/plain');
-      ctx.response.header['content-type'].should.equal('text/plain');
+      ctx.response.header['content-type'].should.equal('text/plain; charset=utf-8');
     })
   })
 
@@ -20,6 +20,24 @@ describe('ctx.type=', function(){
       ctx.response.header['content-type'].should.equal('application/json');
     })
   })
+
+  describe('without a charset', function(){
+    it('should default the charset', function(){
+      var ctx = context();
+      ctx.type = 'text/html';
+      ctx.type.should.equal('text/html');
+      ctx.response.header['content-type'].should.equal('text/html; charset=utf-8');
+    })
+  })
+
+  describe('with a charset', function(){
+    it('should not default the charset', function(){
+      var ctx = context();
+      ctx.type = 'text/html; charset=foo';
+      ctx.type.should.equal('text/html');
+      ctx.response.header['content-type'].should.equal('text/html; charset=foo');
+    })
+  })
 })
 
 describe('ctx.type', function(){