diff --git a/index.js b/index.js
index a871b93f..cb5090fa 100644
--- a/index.js
+++ b/index.js
@@ -1447,7 +1447,7 @@ var cursorTransformsMap = {
 ShareDbMongo.invalidOpVersionError = function(collectionName, id, v) {
   return {
     code: 4101,
-    message: 'Invalid op version ' + collectionName + '.' + id + ' ' + op.v
+    message: 'Invalid op version ' + collectionName + '.' + id + ' ' + v
   };
 };
 ShareDbMongo.invalidCollectionError = function(collectionName) {