diff --git a/hledger-lib/Hledger/Data/Journal.hs b/hledger-lib/Hledger/Data/Journal.hs
index a101212c4..a82a220c7 100644
--- a/hledger-lib/Hledger/Data/Journal.hs
+++ b/hledger-lib/Hledger/Data/Journal.hs
@@ -1228,9 +1228,12 @@ postingFindTag :: TagName -> Posting -> Maybe (TagName, TagValue)
 postingFindTag tagname p = find ((tagname==) . fst) $ postingAllTags p
 
 -- | Apply some account aliases to all posting account names in the journal, as described by accountNameApplyAliases.
--- This can raise an error arising from a bad replacement pattern in a regular expression alias.
-journalApplyAliases :: [AccountAlias] -> Journal -> Journal
-journalApplyAliases aliases j = j{jtxns = map (transactionApplyAliases aliases) $ jtxns j}  -- PARTIAL:
+-- This can fail due to a bad replacement pattern in a regular expression alias.
+journalApplyAliases :: [AccountAlias] -> Journal -> Either RegexError Journal
+journalApplyAliases aliases j = 
+  case mapM (transactionApplyAliases aliases) $ jtxns j of
+    Right ts -> Right j{jtxns = ts}
+    Left err -> Left err
   
 -- -- | Build a database of market prices in effect on the given date,
 -- -- from the journal's price directives.
diff --git a/hledger-lib/Hledger/Data/Posting.hs b/hledger-lib/Hledger/Data/Posting.hs
index fd401e319..57a8ce7d9 100644
--- a/hledger-lib/Hledger/Data/Posting.hs
+++ b/hledger-lib/Hledger/Data/Posting.hs
@@ -291,14 +291,15 @@ concatAccountNames as = accountNameWithPostingType t $ T.intercalate ":" $ map a
     where t = headDef RegularPosting $ filter (/= RegularPosting) $ map accountNamePostingType as
 
 -- | Apply some account aliases to the posting's account name, as described by accountNameApplyAliases.
--- This can raise an error arising from a bad replacement pattern in a regular expression alias.
-postingApplyAliases :: [AccountAlias] -> Posting -> Posting
+-- This can fail due to a bad replacement pattern in a regular expression alias.
+postingApplyAliases :: [AccountAlias] -> Posting -> Either RegexError Posting
 postingApplyAliases aliases p@Posting{paccount} =
   case accountNameApplyAliases aliases paccount of
-    Right a -> p{paccount=a}
-    Left e  -> error' err  -- PARTIAL:
+    Right a -> Right p{paccount=a}
+    Left e  -> Left err
       where
-        err = "problem in account aliases:\n" ++ pshow aliases ++ "\n applied to account name: "++T.unpack paccount++"\n "++e
+        err = "problem while applying account aliases:\n" ++ pshow aliases 
+          ++ "\n to account name: "++T.unpack paccount++"\n "++e
 
 -- | Rewrite an account name using all matching aliases from the given list, in sequence.
 -- Each alias sees the result of applying the previous aliases.
diff --git a/hledger-lib/Hledger/Data/Transaction.hs b/hledger-lib/Hledger/Data/Transaction.hs
index 4dc562104..e0b5b090e 100644
--- a/hledger-lib/Hledger/Data/Transaction.hs
+++ b/hledger-lib/Hledger/Data/Transaction.hs
@@ -593,10 +593,12 @@ transactionToCost :: M.Map CommoditySymbol AmountStyle -> Transaction -> Transac
 transactionToCost styles t@Transaction{tpostings=ps} = t{tpostings=map (postingToCost styles) ps}
 
 -- | Apply some account aliases to all posting account names in the transaction, as described by accountNameApplyAliases.
--- This can raise an error arising from a bad replacement pattern in a regular expression alias.
-transactionApplyAliases :: [AccountAlias] -> Transaction -> Transaction
+-- This can fail due to a bad replacement pattern in a regular expression alias.
+transactionApplyAliases :: [AccountAlias] -> Transaction -> Either RegexError Transaction
 transactionApplyAliases aliases t =
-  txnTieKnot $ t{tpostings = map (postingApplyAliases aliases) $ tpostings t}  -- PARTIAL:
+  case mapM (postingApplyAliases aliases) $ tpostings t of
+    Right ps -> Right $ txnTieKnot $ t{tpostings=ps}
+    Left err -> Left err
 
 -- tests
 
diff --git a/hledger-lib/Hledger/Read/Common.hs b/hledger-lib/Hledger/Read/Common.hs
index 358c9c150..f192d1383 100644
--- a/hledger-lib/Hledger/Read/Common.hs
+++ b/hledger-lib/Hledger/Read/Common.hs
@@ -296,10 +296,11 @@ parseAndFinaliseJournal' parser iopts f txt = do
   -- see notes above
   case ep of
     Left e   -> throwError $ customErrorBundlePretty e
-    Right pj -> journalFinalise iopts f txt $
-                -- apply any command line account aliases. Can fail with a bad replacement pattern.
-                journalApplyAliases (aliasesFromOpts iopts) $  -- PARTIAL:
-                pj
+    Right pj -> 
+      -- apply any command line account aliases. Can fail with a bad replacement pattern.
+      case journalApplyAliases (aliasesFromOpts iopts) pj of
+        Left e    -> throwError e
+        Right pj' -> journalFinalise iopts f txt pj'
 
 -- | Post-process a Journal that has just been parsed or generated, in this order:
 --
diff --git a/hledger-lib/Hledger/Read/CsvReader.hs b/hledger-lib/Hledger/Read/CsvReader.hs
index ab93a3ce8..6357a9ca0 100644
--- a/hledger-lib/Hledger/Read/CsvReader.hs
+++ b/hledger-lib/Hledger/Read/CsvReader.hs
@@ -108,15 +108,16 @@ parse iopts f t = do
   let rulesfile = mrules_file_ iopts
   r <- liftIO $ readJournalFromCsv rulesfile f t
   case r of Left e   -> throwError e
-            Right pj -> journalFinalise iopts{ignore_assertions_=True} f t pj''
-              where
-                -- journalFinalise assumes the journal's items are
-                -- reversed, as produced by JournalReader's parser.
-                -- But here they are already properly ordered. So we'd
-                -- better preemptively reverse them once more. XXX inefficient
-                pj' = journalReverse pj
-                -- apply any command line account aliases. Can fail with a bad replacement pattern.
-                pj'' = journalApplyAliases (aliasesFromOpts iopts)  pj'  -- PARTIAL:
+            Right pj ->
+              -- journalFinalise assumes the journal's items are
+              -- reversed, as produced by JournalReader's parser.
+              -- But here they are already properly ordered. So we'd
+              -- better preemptively reverse them once more. XXX inefficient
+              let pj' = journalReverse pj
+              -- apply any command line account aliases. Can fail with a bad replacement pattern.
+              in case journalApplyAliases (aliasesFromOpts iopts) pj' of
+                  Left e -> throwError e
+                  Right pj'' -> journalFinalise iopts{ignore_assertions_=True} f t pj''
 
 --- ** reading rules files
 --- *** rules utilities
diff --git a/hledger-lib/Hledger/Utils/Regex.hs b/hledger-lib/Hledger/Utils/Regex.hs
index fe11df485..d96d72fba 100644
--- a/hledger-lib/Hledger/Utils/Regex.hs
+++ b/hledger-lib/Hledger/Utils/Regex.hs
@@ -147,7 +147,9 @@ toRegexCI' = either error' id . toRegexCI
 -- | A replacement pattern. May include numeric backreferences (\N).
 type Replacement = String
 
--- | An regular expression compilation/processing error message.
+-- | An error message arising during a regular expression operation.
+-- Eg: trying to compile a malformed regular expression, or
+-- trying to apply a malformed replacement pattern.
 type RegexError = String
 
 -- helpers