diff --git a/hledger-lib/Hledger/Data/Journal.hs b/hledger-lib/Hledger/Data/Journal.hs
index 5debb5e26d08..28d8be8d31fa 100644
--- a/hledger-lib/Hledger/Data/Journal.hs
+++ b/hledger-lib/Hledger/Data/Journal.hs
@@ -909,12 +909,9 @@ journalInferMarketPricesFromTransactions j =
        journalPostings j
    }
 
--- | Convert all this journal's amounts to cost using the transaction prices, if any.
--- The journal's commodity styles are applied to the resulting amounts.
+-- | Convert all this journal's amounts to cost using their attached prices, if any.
 journalToCost :: ConversionOp -> Journal -> Journal
-journalToCost cost j@Journal{jtxns=ts} = j{jtxns=map (transactionToCost styles cost) ts}
-  where
-    styles = journalCommodityStyles j
+journalToCost cost j@Journal{jtxns=ts} = j{jtxns=map (transactionToCost cost) ts}
 
 -- | Add equity postings inferred from costs, where needed and possible.
 -- See hledger manual > Cost reporting.
diff --git a/hledger-lib/Hledger/Data/Posting.hs b/hledger-lib/Hledger/Data/Posting.hs
index 356c77aaa1ff..1f2e2c90d122 100644
--- a/hledger-lib/Hledger/Data/Posting.hs
+++ b/hledger-lib/Hledger/Data/Posting.hs
@@ -447,14 +447,13 @@ postingApplyValuation :: PriceOracle -> M.Map CommoditySymbol AmountStyle -> Day
 postingApplyValuation priceoracle styles periodlast today v p =
     postingTransformAmount (mixedAmountApplyValuation priceoracle styles periodlast today (postingDate p) v) p
 
--- | Maybe convert this 'Posting's amount to cost, and apply apply appropriate
--- amount styles.
-postingToCost :: M.Map CommoditySymbol AmountStyle -> ConversionOp -> Posting -> Maybe Posting
-postingToCost _      NoConversionOp p = Just p
-postingToCost styles ToCost         p
+-- | Maybe convert this 'Posting's amount to cost.
+postingToCost :: ConversionOp -> Posting -> Maybe Posting
+postingToCost NoConversionOp p = Just p
+postingToCost ToCost         p
     -- If this is a conversion posting with a matched transaction price posting, ignore it
     | "_conversion-matched" `elem` map fst (ptags p) && noCost = Nothing
-    | otherwise = Just $ postingTransformAmount (mixedAmountSetStyles styles . mixedAmountCost) p
+    | otherwise = Just $ postingTransformAmount mixedAmountCost p
   where
     noCost = (not . any (isJust . aprice) . amountsRaw) $ pamount p
 
diff --git a/hledger-lib/Hledger/Data/Transaction.hs b/hledger-lib/Hledger/Data/Transaction.hs
index aebddef8df7f..0fc41720089a 100644
--- a/hledger-lib/Hledger/Data/Transaction.hs
+++ b/hledger-lib/Hledger/Data/Transaction.hs
@@ -221,10 +221,9 @@ transactionApplyValuation :: PriceOracle -> M.Map CommoditySymbol AmountStyle ->
 transactionApplyValuation priceoracle styles periodlast today v =
   transactionTransformPostings (postingApplyValuation priceoracle styles periodlast today v)
 
--- | Maybe convert this 'Transaction's amounts to cost and apply the
--- appropriate amount styles.
-transactionToCost :: M.Map CommoditySymbol AmountStyle -> ConversionOp -> Transaction -> Transaction
-transactionToCost styles cost t = t{tpostings = mapMaybe (postingToCost styles cost) $ tpostings t}
+-- | Maybe convert this 'Transaction's amounts to cost.
+transactionToCost :: ConversionOp -> Transaction -> Transaction
+transactionToCost cost t = t{tpostings = mapMaybe (postingToCost cost) $ tpostings t}
 
 -- | Add inferred equity postings to a 'Transaction' using transaction prices.
 transactionAddInferredEquityPostings :: Bool -> AccountName -> Transaction -> Transaction