diff --git a/src/controllers/groups.js b/src/controllers/groups.js
index 4efd8c65bd..c31c35d107 100644
--- a/src/controllers/groups.js
+++ b/src/controllers/groups.js
@@ -33,7 +33,7 @@ var populateQuery = function(type, q){
   q.populate({
     path: 'challenges',
     select: challengeFields,
-    options: {sort: [['timestamp',-1]]}
+    options: {sort: {'timestamp': -1}}
   });
   return q;
 }