diff --git a/src/ajax.js b/src/ajax.js
index 1402c5af0..2612fa9da 100644
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -256,11 +256,11 @@
       return xhr
     }
 
-    if (settings.xhrFields) for (name in settings.xhrFields) xhr[name] = settings.xhrFields[name]
-
     var async = 'async' in settings ? settings.async : true
     xhr.open(settings.type, settings.url, async, settings.username, settings.password)
 
+    if (settings.xhrFields) for (name in settings.xhrFields) xhr[name] = settings.xhrFields[name]
+
     for (name in headers) nativeSetHeader.apply(xhr, headers[name])
 
     if (settings.timeout > 0) abortTimeout = setTimeout(function(){