diff --git a/lib/application.js b/lib/application.js
index 2246c62..8bb3642 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -41,7 +41,6 @@ function Application() {
   if (!(this instanceof Application)) return new Application;
   this.env = process.env.NODE_ENV || 'development';
   this.subdomainOffset = 2;
-  this.poweredBy = true;
   this.middleware = [];
   this.context = Object.create(context);
   this.request = Object.create(request);
@@ -82,7 +81,6 @@ app.inspect =
 app.toJSON = function(){
   return only(this, [
     'subdomainOffset',
-    'poweredBy',
     'env'
   ]);
 };
@@ -174,8 +172,6 @@ app.onerror = function(err){
  */
 
 function *respond(next) {
-  if (this.app.poweredBy) this.set('X-Powered-By', 'koa');
-
   yield *next;
 
   // allow bypassing koa
diff --git a/test/application.js b/test/application.js
index 25a8035..8bfef59 100644
--- a/test/application.js
+++ b/test/application.js
@@ -57,7 +57,6 @@ describe('app.toJSON()', function(){
 
     obj.should.eql({
       subdomainOffset: 2,
-      poweredBy: true,
       env: 'test'
     });
   })