diff --git a/lib/newfol/database.py b/lib/newfol/database.py
index 85d6c1a..1f6d7d1 100644
--- a/lib/newfol/database.py
+++ b/lib/newfol/database.py
@@ -562,7 +562,9 @@ class Database:
 
     def upgrade(self, txntype=None, notify=None, version=None):
         if notify is None:
-            notify = lambda x: x
+
+            def notify(x):
+                x
         if txntype is None:
             txntype = list(self._schema.transaction_types())
         elif isinstance(txntype, str):