diff --git a/src/dsdk/mongo.py b/src/dsdk/mongo.py
index 1667749..fba6fd7 100644
--- a/src/dsdk/mongo.py
+++ b/src/dsdk/mongo.py
@@ -144,7 +144,7 @@ def store_evidence(self, batch: Batch, *args, **kwargs) -> None:
             with self.open_mongo() as database:
                 collection = database[key]
                 result = insert_many(collection, docs)
-                actual = len(result.inserted.ids)
+                actual = len(result.inserted_ids)
                 expected = columns.shape[0]
                 assert actual == expected, self.RESULTSET_ERROR % (
                     database.name,