diff --git a/lib/client.js b/lib/client.js
index 471aedc4ac..603142d1ae 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -59,26 +59,40 @@ Client.prototype.setup = function(){
  */
 
 Client.prototype.connect = function(name){
+  var self = this;
   debug('connecting to namespace %s', name);
-  if (!this.server.nsps[name]) {
-    this.packet({ type: parser.ERROR, nsp: name, data : 'Invalid namespace'});
-    return;
+
+  function connectNamespace() {
+    var nsp = self.server.of(name);
+    if ('/' != name && !self.nsps['/']) {
+      self.connectBuffer.push(name);
+      return;
+    }
+
+    var socket = nsp.add(self, function(){
+      self.sockets.push(socket);
+      self.nsps[nsp.name] = socket;
+
+      if ('/' == nsp.name && self.connectBuffer.length > 0) {
+        self.connectBuffer.forEach(self.connect, self);
+        self.connectBuffer = [];
+      }
+    });
   }
-  var nsp = this.server.of(name);
-  if ('/' != name && !this.nsps['/']) {
-    this.connectBuffer.push(name);
+
+  if (self.server.nsps[name]) {
+    // Namespace already created, connect
+    connectNamespace();
     return;
   }
 
-  var self = this;
-  var socket = nsp.add(this, function(){
-    self.sockets.push(socket);
-    self.nsps[nsp.name] = socket;
-
-    if ('/' == nsp.name && self.connectBuffer.length > 0) {
-      self.connectBuffer.forEach(self.connect, self);
-      self.connectBuffer = [];
+  self.server.checkNamespace(name, function(allow) {
+    if (allow) {
+      connectNamespace();
+      return
     }
+
+    self.packet({ type: parser.ERROR, nsp: name, data : 'Invalid namespace'});
   });
 };
 
diff --git a/lib/index.js b/lib/index.js
index 27634923c5..bb84b8bcc8 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -43,6 +43,7 @@ function Server(srv, opts){
   }
   opts = opts || {};
   this.nsps = {};
+  this.nspValidators = [];
   this.path(opts.path || '/socket.io');
   this.serveClient(false !== opts.serveClient);
   this.adapter(opts.adapter || Adapter);
@@ -137,6 +138,53 @@ Server.prototype.set = function(key, val){
   return this;
 };
 
+/**
+ * Sets up server middleware to validate incoming namespaces not already created on the server.
+ *
+ * @return {Server} self
+ * @api public
+ */
+
+Server.prototype.useNamespaceValidator = function(fn){
+  this.nspValidators.push(fn);
+  return this;
+};
+
+/**
+ * Executes the middleware for an incoming namespace not already created on the server.
+ *
+ * @param name of incomming namespace
+ * @param {Function} last fn call in the middleware
+ * @api private
+ */
+
+Server.prototype.checkNamespace = function(name, fn){
+  var fns = this.nspValidators.slice(0);
+  if (!fns.length) return fn(false);
+
+  var namespaceAllowed = false; // Deny unknown namespaces by default
+
+  function run(i){
+    fns[i](name, function(err, allow){
+      // upon error, short-circuit
+      if (err) return fn(false);
+
+      // if one piece of middleware explicitly denies namespace, short-circuit
+      if (allow === false) return fn(false);
+
+      namespaceAllowed = namespaceAllowed || allow === true;
+
+      // if no middleware left, summon callback
+      if (!fns[i + 1]) return fn(namespaceAllowed);
+
+      // go on to next
+      run(i + 1);
+    });
+  }
+
+  run(0);
+};
+
 /**
  * Sets the client serving path.
  *
diff --git a/test/socket.io.js b/test/socket.io.js
index c7fbe9a387..2114ee98b3 100644
--- a/test/socket.io.js
+++ b/test/socket.io.js
@@ -817,6 +817,78 @@ describe('socket.io', function(){
         });
       });
     });
+
+    it('should allow connections to dynamic namespaces', function(done){
+      var srv = http();
+      var sio = io(srv);
+      srv.listen(function(){
+        var namespace = '/dynamic';
+        var dynamic = client(srv,namespace);
+        sio.useNamespaceValidator(function(nsp, next) {
+          expect(nsp).to.be(namespace);
+          next(null, true);
+        });
+        dynamic.on('error', function(err) {
+          expect().fail();
+        });
+        dynamic.on('connect', function() {
+          expect(sio.nsps[namespace]).to.be.a(Namespace);
+          expect(sio.nsps[namespace].sockets.length).to.be(1);
+          done();
+        });
+      });
+    });
+
+    it('should not allow connections to dynamic namespaces if not supported', function(done){
+      var srv = http();
+      var sio = io(srv);
+      srv.listen(function(){
+        var namespace = '/dynamic';
+        sio.useNamespaceValidator(function(nsp, next) {
+          expect(nsp).to.be(namespace);
+          next(null, false);
+        });
+        sio.on('connect', function(socket) {
+          if (socket.nsp.name === namespace) {
+            expect().fail();
+          }
+        });
+
+        var dynamic = client(srv,namespace);
+        dynamic.on('connect', function(){
+          expect().fail();
+        });
+        dynamic.on('error', function(err) {
+          expect(err).to.be("Invalid namespace");
+          done();
+        });
+      });
+    });
+    it('should not allow connections to dynamic namespaces if there is an error', function(done){
+      var srv = http();
+      var sio = io(srv);
+      srv.listen(function(){
+        var namespace = '/dynamic';
+        sio.useNamespaceValidator(function(nsp, next) {
+          expect(nsp).to.be(namespace);
+          next(new Error(), true);
+        });
+        sio.on('connect', function(socket) {
+          if (socket.nsp.name === namespace) {
+            expect().fail();
+          }
+        });
+
+        var dynamic = client(srv,namespace);
+        dynamic.on('connect', function(){
+          expect().fail();
+        });
+        dynamic.on('error', function(err) {
+          expect(err).to.be("Invalid namespace");
+          done();
+        });
+      });
+    });
   });
 
   describe('socket', function(){