diff --git a/lib/collection.js b/lib/collection.js
index ba40d4a..1cc3dc1 100644
--- a/lib/collection.js
+++ b/lib/collection.js
@@ -155,7 +155,7 @@ SkinCollection.prototype.updateById = function (id, doc, callback) {
   var _this = this;
   if (callback) {
     callback = function(error, res) {
-      oldCb.call(_this, error, res.result);
+      oldCb.call(_this, error, !!res ? res.result : null);
     };
   }
   return this._operateById('update', id, [id, doc, callback]);
@@ -173,7 +173,7 @@ SkinCollection.prototype.removeById = function (id, callback) {
   var _this = this;
   if (callback) {
     callback = function(error, res) {
-      oldCb.call(_this, error, res.result.n);
+      oldCb.call(_this, error, !!res ? res.result.n : null);
     };
   }
   return this._operateById('remove', id, [id, callback]);