diff --git a/conservancy_beancount/data.py b/conservancy_beancount/data.py
index ff865242e24d4d1ae76669cb047228cc84c50d6f..b076977fda3ff42f20495df04dbeed810cb15917 100644
--- a/conservancy_beancount/data.py
+++ b/conservancy_beancount/data.py
@@ -27,6 +27,7 @@ import functools
 from beancount.core import account as bc_account
 from beancount.core import amount as bc_amount
 from beancount.core import convert as bc_convert
+from beancount.core import position as bc_position
 
 from typing import (
     cast,
@@ -269,6 +270,7 @@ class Posting(BasePosting):
 
     account: Account
     units: Amount
+    cost: Optional[bc_position.Cost]
     # mypy correctly complains that our MutableMapping is not compatible
     # with Beancount's meta type declaration of Optional[Dict]. IMO
     # Beancount's type declaration is a smidge too specific: I think its type