diff --git a/lib/carto/tree/filterset.js b/lib/carto/tree/filterset.js
index fa57dc0..0fd7ba7 100644
--- a/lib/carto/tree/filterset.js
+++ b/lib/carto/tree/filterset.js
@@ -92,7 +92,7 @@ tree.Filterset.prototype.toJS = function(env) {
     }
 
     var attrs = "data";
-    return attrs + "." + filter.key  + " " + op + " " + val;
+    return attrs + "." + filter.key.value  + " " + op + " " + val;
   }).join(' && ');
 }