diff --git a/lib/request.js b/lib/request.js
index 719e99b..ec1c7a2 100644
--- a/lib/request.js
+++ b/lib/request.js
@@ -577,6 +577,7 @@ module.exports = {
    */
 
   inspect: function(){
+    if (!this.req) return;
     return this.toJSON();
   },
 
diff --git a/lib/response.js b/lib/response.js
index 07d8291..7c4f545 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -432,6 +432,7 @@ module.exports = {
    */
 
   inspect: function(){
+    if (!this.res) return;
     var o = this.toJSON();
     o.body = this.body;
     return o;
diff --git a/test/application.js b/test/application.js
index f2c56df..324ea2b 100644
--- a/test/application.js
+++ b/test/application.js
@@ -61,6 +61,14 @@ describe('app.toJSON()', function(){
   })
 })
 
+describe('app.inspect()', function(){
+  it('should work', function(){
+    var app = koa();
+    var util = require('util');
+    var str = util.inspect(app);
+  })
+})
+
 describe('app.use(fn)', function(){
   it('should compose middleware', function(done){
     var app = koa();