diff --git a/lib/carto/tree/rule.js b/lib/carto/tree/rule.js
index 33dbc3d..d63a9ba 100644
--- a/lib/carto/tree/rule.js
+++ b/lib/carto/tree/rule.js
@@ -26,7 +26,7 @@ tree.Rule.prototype.clone = function() {
 };
 
 tree.Rule.prototype.updateID = function() {
-    return this.id = this.zoom + '#' + this.name;
+    return this.id = this.zoom + '#' + this.instance + '#' + this.name;
 };
 
 tree.Rule.prototype.toString = function() {