diff --git a/lib/cartodb/cartodb_windshaft.js b/lib/cartodb/cartodb_windshaft.js
index c8712a25..134f6010 100644
--- a/lib/cartodb/cartodb_windshaft.js
+++ b/lib/cartodb/cartodb_windshaft.js
@@ -80,7 +80,7 @@ var CartodbWindshaft = function(serverOptions) {
             },
             function(err, data){
                 if (err){
-                    res.send(err.message, 500);
+                    res.send({error: err.message}, 500);
                 } else {
                     res.send({infowindow: data}, 200);
                 }