diff --git a/hledger-lib/Hledger/Read/JournalReader.hs b/hledger-lib/Hledger/Read/JournalReader.hs
index ec3861c57..225d8ce04 100644
--- a/hledger-lib/Hledger/Read/JournalReader.hs
+++ b/hledger-lib/Hledger/Read/JournalReader.hs
@@ -101,10 +101,14 @@ parse _ = parseJournalWith journal
 genericSourcePos :: SourcePos -> GenericSourcePos
 genericSourcePos p = GenericSourcePos (sourceName p) (sourceLine p) (sourceColumn p)
 
--- | Flatten a list of JournalUpdate's into a single equivalent one.
+-- | Flatten a list of JournalUpdate's (journal-transforming
+-- monadic actions which can do IO or raise an exception) into a
+-- single equivalent action.
 combineJournalUpdates :: [JournalUpdate] -> JournalUpdate
 combineJournalUpdates us = liftM (foldl' (\acc new x -> new (acc x)) id) $ sequence us
 -- XXX may be contributing to excessive stack use
+--combineJournalUpdates us = foldl' (flip (.)) id <$> sequence us
+
 -- cf http://neilmitchell.blogspot.co.uk/2015/09/detecting-space-leaks.html
 -- $ ./devprof +RTS -K576K -xc
 -- *** Exception (reporting due to +RTS -xc): (THUNK_STATIC), stack trace: