diff --git a/lib/application.js b/lib/application.js
index c59a089..1ef6eef 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -215,7 +215,7 @@ function *respond(next){
   }
 
   // Stream body
-  if (body instanceof Stream) {
+  if ('function' == typeof body.pipe) {
     if (!~body.listeners('error').indexOf(this.onerror)) body.on('error', this.onerror);
 
     if (head) {
diff --git a/lib/response.js b/lib/response.js
index a3ea91b..01be800 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -133,7 +133,7 @@ module.exports = {
     }
 
     // stream
-    if (val instanceof Stream) {
+    if ('function' == typeof val.pipe) {
       if (setType) this.type = 'bin';
       return;
     }