diff --git a/lib/application.js b/lib/application.js
index e7c5a26..c787793 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -209,7 +209,7 @@ function respond(next){
 
     // body: json
     body = JSON.stringify(body, null, this.app.jsonSpaces);
-    this.set('Content-Length', body.length);
+    this.set('Content-Length', Buffer.byteLength(body));
     this.set('Content-Type', 'application/json');
     if (head) return res.end();
     res.end(body);