diff --git a/pydantic_mongo/abstract_repository.py b/pydantic_mongo/abstract_repository.py
index 233e634..bfa307d 100644
--- a/pydantic_mongo/abstract_repository.py
+++ b/pydantic_mongo/abstract_repository.py
@@ -71,6 +71,8 @@ def to_document(model: T) -> dict:
         data.pop("id")
         if model.id:
             data["_id"] = model.id
+        if model.v:
+            data["__v"] = model.v
         return data
 
     def __map_id(self, data: dict) -> dict: