From a4dad95be3e0051da7109aa016e9023ba714769b Mon Sep 17 00:00:00 2001
From: Aaron Heckmann <aaron.heckmann+github@gmail.com>
Date: Tue, 15 Mar 2011 09:01:24 -0400
Subject: [PATCH] EventEmitter#once only takes instanceof function

---
 lib/events.js | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/events.js b/lib/events.js
index 2d2d5d19cb..9b13c80f8e 100644
--- a/lib/events.js
+++ b/lib/events.js
@@ -137,6 +137,10 @@ EventEmitter.prototype.addListener = function(type, listener) {
 EventEmitter.prototype.on = EventEmitter.prototype.addListener;
 
 EventEmitter.prototype.once = function(type, listener) {
+  if ('function' !== typeof listener) {
+    throw new Error('.once only takes instances of Function');
+  }
+
   var self = this;
   self.on(type, function g() {
     self.removeListener(type, g);