diff --git a/lib/cartodb/controllers/map.js b/lib/cartodb/controllers/map.js
index 9c2168d5..6650fd20 100644
--- a/lib/cartodb/controllers/map.js
+++ b/lib/cartodb/controllers/map.js
@@ -73,7 +73,7 @@ MapController.prototype.composeCreateMapMiddleware = function (useTemplate = fal
         allowQueryParams(['aggregation']),
         this.prepareContext,
         initProfiler(isTemplateInstantiation),
-        this.checkJsonContentType(),
+        checkJsonContentType(),
         useTemplate ? this.checkInstantiteLayergroup() : this.checkCreateLayergroup(),
         useTemplate ? this.getTemplate() : this.prepareAdapterMapConfig(),
         useTemplate ? this.instantiateLayergroup() : this.createLayergroup(),
@@ -107,7 +107,7 @@ function initProfiler (isTemplateInstantiation) {
     };
 }
 
-MapController.prototype.checkJsonContentType = function () {
+function checkJsonContentType () {
     return function checkJsonContentTypeMiddleware(req, res, next) {
         if (req.method === 'POST' && !req.is('application/json')) {
             return next(new Error('POST data must be of type application/json'));
@@ -117,7 +117,7 @@ MapController.prototype.checkJsonContentType = function () {
 
         next();
     };
-};
+}
 
 MapController.prototype.checkInstantiteLayergroup = function () {
     return function checkInstantiteLayergroupMiddleware(req, res, next) {