diff --git a/brmbar3/schema/0015-shop-buy-for-cash.sql b/brmbar3/schema/0015-shop-buy-for-cash.sql
index 90cb883..aa66260 100644
--- a/brmbar3/schema/0015-shop-buy-for-cash.sql
+++ b/brmbar3/schema/0015-shop-buy-for-cash.sql
@@ -44,12 +44,15 @@ DECLARE
 	v_buy_rate NUMERIC;
 	v_cost NUMERIC;
 	v_transaction_id public.transactions.id%TYPE;
+	v_item_currency_id public.accounts.currency%TYPE;
 BEGIN
-	-- this could fail and it would generate exception in python
-	-- FIXME: convert v_buy_rate < 0 into python exception
-	v_buy_rate := public.find_buy_rate(i_item_id, i_target_currency_id);
-	-- this could fail and it would generate exception in python, even though it is not used
-	--v_sell_rate := public.find_sell_rate(i_item_id, i_target_currency_id);
+	-- Get item's currency
+	SELECT currency
+		INTO STRICT v_item_currency_id
+		FROM public.accounts
+		WHERE id=i_item_id;
+	-- Get the buy rates from the stored functions
+	v_buy_rate := public.find_buy_rate(v_item_currency_id, i_target_currency_id);
 
 	-- Calculate cost and profit
 	v_cost := i_amount * v_buy_rate;