diff --git a/lib/cartodb/api/map/tile-layergroup-controller.js b/lib/cartodb/api/map/tile-layergroup-controller.js
index 229f5d00..311fec45 100644
--- a/lib/cartodb/api/map/tile-layergroup-controller.js
+++ b/lib/cartodb/api/map/tile-layergroup-controller.js
@@ -42,12 +42,15 @@ module.exports = class TileLayergroupController {
     }
 
     register (mapRouter) {
-        // REGEXP doesn't match with `val`
+        // REGEXP: doesn't match with `val`
         const not = (val) => `(?!${val})([^\/]+?)`;
 
+        // Sadly the path that matches 1 also matches with 2 so we need to tell to express
+        // that performs only the middlewares of the first path that matches
+        // for that we use one array to group all paths.
         mapRouter.get([
-            `/:token/:z/:x/:y@:scale_factor?x.:format`,
-            `/:token/:z/:x/:y.:format`,
+            `/:token/:z/:x/:y@:scale_factor?x.:format`, // 1
+            `/:token/:z/:x/:y.:format`, // 2
             `/:token${not('static')}/:layer/:z/:x/:y.(:format)`
         ], this.middlewares());
     }