diff --git a/src/ajax.js b/src/ajax.js
index 82c499b64..968c67c8a 100644
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -160,7 +160,7 @@ jQuery.extend({
 	},
 
 	ajaxSetup: function( settings ) {
-		jQuery.extend( jQuery.ajaxSettings, settings );
+		jQuery.extend( true, jQuery.ajaxSettings, settings );
 	},
 
 	ajaxSettings: {