diff --git a/alpaca/broker/models/trading.py b/alpaca/broker/models/trading.py
index 3d67b3de..8d271193 100644
--- a/alpaca/broker/models/trading.py
+++ b/alpaca/broker/models/trading.py
@@ -9,4 +9,4 @@ class Order(BaseOrder):
         commission (float): The dollar value commission you want to charge the end user.
     """
 
-    commission: float
+    commission: float | None = None