diff --git a/lib/namespace.js b/lib/namespace.js
index 639e4b1bb5..4524b4bff1 100644
--- a/lib/namespace.js
+++ b/lib/namespace.js
@@ -114,14 +114,17 @@ Namespace.prototype.run = function(socket, fn){
 };
 
 /**
- * Targets a room.
+ * Targets a room when emitting.
  *
- * @api private
+ * @param {String} name
+ * @return {Namespace} self
+ * @api public
  */
 
 Namespace.prototype.to =
-Namespace.prototype.in = function(fn){
-  this.rooms.push(fn);
+Namespace.prototype.in = function(name){
+  this.rooms = this.rooms || [];
+  if (!~this.rooms.indexOf(name)) this.rooms.push(name);
   return this;
 };