diff --git a/backends/mongo.js b/backends/mongo.js
index 264bf6d..ea2ef4d 100644
--- a/backends/mongo.js
+++ b/backends/mongo.js
@@ -37,7 +37,7 @@ MongoBackend.prototype.set = function (options, cb) {
     } else {
       item.expireAt = null
     }
-    backend.coll.updateOne({_id: item.key}, item, {upsert: true}, cb)
+    backend.coll.replaceOne({_id: item.key}, item, {upsert: true}, cb)
   })
 }