diff --git a/lib/restler.js b/lib/restler.js
index 715845a..3ae30d5 100644
--- a/lib/restler.js
+++ b/lib/restler.js
@@ -56,8 +56,10 @@ function Request(uri, options) {
     }
   } else {
     if (typeof this.options.data == 'object') {
-      this.options.data = qs.stringify(this.options.data);
-      this.headers['Content-Type'] = 'application/x-www-form-urlencoded';
+      if (!(this.options.data instanceof Buffer)) {
+        this.options.data = qs.stringify(this.options.data);
+        this.headers['Content-Type'] = 'application/x-www-form-urlencoded';
+      }
       this.headers['Content-Length'] = this.options.data.length;
     }
     if (typeof this.options.data == 'string') {