gistfile1.diff

diff --git a/backbone.js b/backbone.js
index 4217e62..bdc6682 100644
--- a/backbone.js
+++ b/backbone.js
@@ -906,11 +906,11 @@
   // Useful when interfacing with server-side languages like **PHP** that make
   // it difficult to read the body of `PUT` requests.
   Backbone.sync = function(method, model, success, error) {
     var type = methodMap[method];
     var modelJSON = (method === 'create' || method === 'update') ?
-                    JSON.stringify(model.toJSON()) : null;
+                    JSON.stringify(model.toParams ? model.toParams() : model.toJSON()) : null;
 
     // Default JSON-request options.
     var params = {
       url:          getUrl(model),
       type:         type,