diff --git a/fin_defs/__init__.py b/fin_defs/__init__.py
index 08f8581..50865cf 100644
--- a/fin_defs/__init__.py
+++ b/fin_defs/__init__.py
@@ -115,6 +115,7 @@ class CryptoCurrency(Currency):
 class Stock(Asset):
     ticker: str
     exchange: StockExchange
+    nordnet_id: int | None = None
 
     def __post_init__(self):
         if not re.match(RE_TICKER_FORMAT_FLEXIBLE, self.ticker):