diff --git a/ChangeLog b/ChangeLog
deleted file mode 100644
--- a/ChangeLog
+++ /dev/null
@@ -1,18 +0,0 @@
-2022-05-30 v0.0.4
-	* Injecting cabal flags via environment variable. [#13](https://github.com/kazu-yamamoto/hhp/pull/13)
-	* Update to handle sub-libraries in .cabal file. [#14](https://github.com/kazu-yamamoto/hhp/pull/14)
-
-2022-07-21 v0.0.3
-	* fixing test due to hlint change.
-	* supporting GHC 8.10
-
-2019-10-03 v0.0.2
-	* supporting Cabal 3.0 and GHC 8.8.
-
-2019-06-21 v0.0.1
-	* setting PartialTypeSignatures and NamedWildCards for check
-	* Remap save-buffer to hhp-save-buffer [#6](https://github.com/kazu-yamamoto/hhp/pull/6)
-	* using "-fdefer-typed-holes" for check.
-
-2018-12-18 v0.0.0
-	* First release
diff --git a/ChangeLog.md b/ChangeLog.md
new file mode 100644
--- /dev/null
+++ b/ChangeLog.md
@@ -0,0 +1,29 @@
+# ChangeLog for HHP(Happy Haskell Programming)
+
+## 2022-05-30 v1.0.0
+
+- Supporting GHC 9.x only.
+
+## 2022-05-30 v0.0.4
+
+- Injecting cabal flags via environment variable. [#13](https://github.com/kazu-yamamoto/hhp/pull/13)
+- Update to handle sub-libraries in .cabal file. [#14](https://github.com/kazu-yamamoto/hhp/pull/14)
+
+## 2020-07-21 v0.0.3
+
+- fixing test due to hlint change.
+- supporting GHC 8.10
+
+## 2019-10-03 v0.0.2
+
+- supporting Cabal 3.0 and GHC 8.8.
+
+## 2019-06-21 v0.0.1
+
+- setting PartialTypeSignatures and NamedWildCards for check
+- Remap save-buffer to hhp-save-buffer [#6](https://github.com/kazu-yamamoto/hhp/pull/6)
+- using "-fdefer-typed-holes" for check.
+
+## 2018-12-18 v0.0.0
+
+- First release
diff --git a/hhp.cabal b/hhp.cabal
--- a/hhp.cabal
+++ b/hhp.cabal
@@ -1,5 +1,5 @@
 Name:                   hhp
-Version:                1.0.0
+Version:                1.0.1
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -24,7 +24,7 @@
 Data-Files:             Makefile hhp.el hhp-func.el hhp-doc.el hhp-comp.el
                         hhp-check.el hhp-process.el hhp-command.el hhp-info.el
                         hhp-ins-mod.el hhp-indent.el hhp-pkg.el
-Extra-Source-Files:     ChangeLog
+Extra-Source-Files:     ChangeLog.md
                         test/data/*.cabal
                         test/data/*.hs
                         test/data/cabal.sandbox.config.in
diff --git a/lib/Hhp/Browse.hs b/lib/Hhp/Browse.hs
--- a/lib/Hhp/Browse.hs
+++ b/lib/Hhp/Browse.hs
@@ -8,8 +8,11 @@
 import GHC.Core.TyCon (isAlgTyCon)
 import GHC.Core.Type (dropForAlls, splitFunTy_maybe, isPredTy, mkVisFunTy)
 import GHC.Data.FastString (mkFastString)
+import GHC.Driver.Session (initSDocContext)
 import GHC.Types.Name (getOccString)
+import GHC.Utils.Monad (liftIO)
 
+import qualified Control.Exception as E
 import Control.Monad.Catch (SomeException(..), handle, catch)
 import Data.Char (isAlpha)
 import Data.List (sort)
@@ -54,10 +57,16 @@
     -- If CmdLineError is signalled, we assume the user
     -- tried browsing a local module.
     getModule = browsePackageModule `catch` fallback `catch` handler
-    browsePackageModule = G.findModule mdlname mpkgid >>= G.getModuleInfo
+    browsePackageModule = do
+        -- "findModule" of GHC 9.2 or earlier throws CmdLineError.
+        -- But that of GHC 9.4 does not, sigh.
+        mx <- G.findModule mdlname mpkgid >>= G.getModuleInfo
+        case mx of
+          Just _ -> return mx
+          _      -> liftIO $ E.throwIO $ CmdLineError "for GHC 9.4"
     browseLocalModule = handle handler $ do
-      setTargetFiles [mdl]
-      G.findModule mdlname Nothing >>= G.getModuleInfo
+        setTargetFiles [mdl]
+        G.findModule mdlname Nothing >>= G.getModuleInfo
     fallback (CmdLineError _) = browseLocalModule
     fallback _                = return Nothing
     handler (SomeException _) = return Nothing
@@ -119,7 +128,7 @@
 formatType dflag a = showOutputable dflag $ removeForAlls a
 
 showOutputable :: DynFlags -> Type -> String
-showOutputable dflag = unwords . lines . showPage dflag styleUnqualified . pprTypeForUser
+showOutputable dflag = unwords . lines . showPage (initSDocContext dflag styleUnqualified) . pprSigmaType
 
 tyType :: TyCon -> Maybe String
 tyType typ
diff --git a/lib/Hhp/CabalApi.hs b/lib/Hhp/CabalApi.hs
--- a/lib/Hhp/CabalApi.hs
+++ b/lib/Hhp/CabalApi.hs
@@ -24,7 +24,11 @@
 import Distribution.Verbosity (silent)
 import Distribution.Version (Version)
 import Distribution.PackageDescription.Configuration (finalizePD)
+#if MIN_VERSION_Cabal(3,8,0)
+import Distribution.Simple.PackageDescription (readGenericPackageDescription)
+#else
 import Distribution.PackageDescription.Parsec (readGenericPackageDescription)
+#endif
 import Distribution.Types.ComponentRequestedSpec (defaultComponentRequestedSpec)
 import Distribution.Types.Flag (mkFlagAssignment, mkFlagName)
 import Distribution.Types.PackageName (unPackageName)
@@ -36,7 +40,7 @@
 
 import Control.Exception (throwIO)
 import Control.Monad (filterM)
-import Data.Maybe (maybeToList, mapMaybe)
+import Data.Maybe (maybeToList, mapMaybe, fromMaybe)
 import Data.Set (fromList, toList)
 import System.Directory (doesFileExist)
 import System.Environment (lookupEnv)
@@ -59,7 +63,7 @@
   where
     wdir       = cradleCurrentDir cradle
     rdir       = cradleRootDir    cradle
-    Just cfile = cradleCabalFile  cradle
+    cfile      = fromMaybe "error getCompilerOptions" $ cradleCabalFile cradle
     thisPkg    = dropExtension $ takeFileName cfile
     buildInfos = cabalAllBuildInfo pkgDesc
     idirs      = includeDirectories rdir wdir $ cabalSourceDirs buildInfos
diff --git a/lib/Hhp/Doc.hs b/lib/Hhp/Doc.hs
--- a/lib/Hhp/Doc.hs
+++ b/lib/Hhp/Doc.hs
@@ -5,27 +5,25 @@
   , styleUnqualified
   ) where
 
-import GHC (Ghc, DynFlags, getPrintUnqual, pprCols)
-import GHC.Utils.Outputable (PprStyle, SDoc, neverQualify, runSDoc, PrintUnqualified, PprStyle, Depth(..), mkUserStyle)
-import GHC.Driver.Session (initSDocContext)
+import GHC (Ghc, getPrintUnqual)
+import GHC.Utils.Outputable (PprStyle, SDoc, neverQualify, runSDoc, PrintUnqualified, PprStyle, Depth(..), mkUserStyle, sdocLineLength, SDocContext)
 import GHC.Utils.Ppr (Mode(..), Style(..), renderStyle, style)
 
 import Hhp.Gap
 
 ----------------------------------------------------------------
 
-showPage :: DynFlags -> PprStyle -> SDoc -> String
+showPage :: SDocContext -> SDoc -> String
 showPage = showSDocWithMode pagemode
 
-showOneLine :: DynFlags -> PprStyle -> SDoc -> String
+showOneLine :: SDocContext -> SDoc -> String
 showOneLine = showSDocWithMode OneLineMode
 
-showSDocWithMode :: Mode -> DynFlags -> PprStyle -> SDoc -> String
-showSDocWithMode md dflags pprstyle sdoc = renderStyle style' doc
+showSDocWithMode :: Mode -> SDocContext -> SDoc -> String
+showSDocWithMode md ctx sdoc = renderStyle style' doc
   where
-    ctx = initSDocContext dflags pprstyle
     doc = runSDoc sdoc ctx
-    style' = style { mode = md, lineLength = pprCols dflags }
+    style' = style { mode = md, lineLength = sdocLineLength ctx }
 
 ----------------------------------------------------------------
 
diff --git a/lib/Hhp/Find.hs b/lib/Hhp/Find.hs
--- a/lib/Hhp/Find.hs
+++ b/lib/Hhp/Find.hs
@@ -13,6 +13,7 @@
 import GHC.Unit.Info (UnitInfo, unitExposedModules, mkUnit)
 import GHC.Unit.State (listUnitInfo, UnitState)
 import GHC.Utils.Outputable (ppr)
+import GHC.Driver.Session (initSDocContext)
 
 import Control.DeepSeq (force)
 import Control.Monad.Catch (SomeException(..), catch)
@@ -71,7 +72,7 @@
   where
     mdl = G.moduleNameString (G.moduleName m)
     names = G.modInfoExports inf
-    toStr = showOneLine dflag styleUnqualified . ppr
+    toStr = showOneLine (initSDocContext dflag styleUnqualified) . ppr
 
 packageModules :: UnitState -> [Module]
 packageModules us = concatMap fromUnitInfo $ listUnitInfo us
diff --git a/lib/Hhp/GHCApi.hs b/lib/Hhp/GHCApi.hs
--- a/lib/Hhp/GHCApi.hs
+++ b/lib/Hhp/GHCApi.hs
@@ -148,7 +148,7 @@
 -- | Set the files as targets and load them.
 setTargetFiles :: [FilePath] -> Ghc ()
 setTargetFiles files = do
-    targets <- forM files $ \file -> G.guessTarget file Nothing
+    targets <- forM files $ \file -> guessTarget file
     G.setTargets targets
     void $ G.load LoadAllTargets
 
diff --git a/lib/Hhp/Gap.hs b/lib/Hhp/Gap.hs
--- a/lib/Hhp/Gap.hs
+++ b/lib/Hhp/Gap.hs
@@ -20,6 +20,10 @@
   , ErrorMessages
   , locA
   , LOC
+  , guessTarget
+  , pprSigmaType
+  , getMessages
+  , hsPatType
   ) where
 
 import GHC (Ghc, DynFlags(..), GhcLink(..))
@@ -29,17 +33,66 @@
 import GHC.Driver.Session (supportedLanguagesAndExtensions)
 import GHC.Utils.Outputable (SDoc)
 
-#if __GLASGOW_HASKELL__ >= 902
+#if __GLASGOW_HASKELL__ >= 904
 ----------------------------------------------------------------
 import GHC (Backend(..), pushLogHookM)
-import GHC.Types.TyThing.Ppr
-import GHC.Types.TyThing (implicitTyThings)
 import GHC.Driver.Env (hsc_units)
+import GHC.Driver.Errors.Types (ErrorMessages, GhcMessage)
+import GHC.Hs.Syn.Type (hsPatType)
+import GHC.Parser.Annotation (locA, LocatedA)
 import GHC.Platform.Host (hostPlatformArchOS)
-import GHC.Utils.Logger (LogAction)
-import GHC.Utils.Error (ErrorMessages, pprLocMsgEnvelope, MsgEnvelope, DecoratedSDoc)
+import GHC.Tc.Utils.TcType (pprSigmaType)
+import GHC.Types.Error (getMessages)
 import GHC.Types.SourceError (SourceError, srcErrorMessages)
+import GHC.Types.TyThing (implicitTyThings)
+import GHC.Types.TyThing.Ppr
+import GHC.Utils.Error (pprLocMsgEnvelope, MsgEnvelope)
+import GHC.Utils.Logger (LogAction)
+
+pagemode :: Mode
+pagemode = PageMode True
+
+getUnitState :: Ghc UnitState
+getUnitState = hsc_units <$> G.getSession
+
+languagesAndExtensions :: [String]
+languagesAndExtensions = supportedLanguagesAndExtensions hostPlatformArchOS
+
+setEmptyLogger :: DynFlags -> DynFlags
+setEmptyLogger = id
+
+-- we don't want to generate object code so we compile to bytecode
+-- (HscInterpreted) which implies LinkInMemory
+-- HscInterpreted
+setLinkerOptions :: DynFlags -> DynFlags
+setLinkerOptions df = df {
+    ghcLink = LinkInMemory
+  , backend = Interpreter
+  }
+
+setLogger :: LogAction -> Ghc ()
+setLogger logaction = pushLogHookM (\__defaultLogAction -> logaction)
+
+pprLocErrMessage :: MsgEnvelope GhcMessage -> SDoc
+pprLocErrMessage = pprLocMsgEnvelope
+
+type LOC = LocatedA
+
+guessTarget :: G.GhcMonad m => String -> m G.Target
+guessTarget file = G.guessTarget file Nothing Nothing
+----------------------------------------------------------------
+#elif __GLASGOW_HASKELL__ >= 902
+----------------------------------------------------------------
+import GHC (Backend(..), pushLogHookM)
+import GHC.Driver.Env (hsc_units)
 import GHC.Parser.Annotation (locA, LocatedA)
+import GHC.Platform.Host (hostPlatformArchOS)
+import GHC.Tc.Utils.Zonk (hsPatType)
+import GHC.Types.SourceError (SourceError, srcErrorMessages)
+import GHC.Types.TyThing (implicitTyThings)
+import GHC.Types.TyThing.Ppr
+import GHC.Utils.Error (ErrorMessages, DecoratedSDoc, pprLocMsgEnvelope, MsgEnvelope)
+import GHC.Utils.Logger (LogAction)
 
 pagemode :: Mode
 pagemode = PageMode True
@@ -69,17 +122,27 @@
 pprLocErrMessage = pprLocMsgEnvelope
 
 type LOC = LocatedA
+
+guessTarget :: G.GhcMonad m => String -> m G.Target
+guessTarget file = G.guessTarget file Nothing
+
+pprSigmaType :: G.Type -> SDoc
+pprSigmaType = pprTypeForUser
+
+getMessages :: a -> a
+getMessages = id
+
 ----------------------------------------------------------------
 #else
 ----------------------------------------------------------------
 import GHC (HscTarget(..), getSessionDynFlags, setSessionDynFlags, Located)
 import GHC.Core.Ppr.TyThing
+import GHC.Data.Bag (Bag)
 import GHC.Driver.Session (LogAction)
-import GHC.Driver.Types (implicitTyThings)
+import GHC.Driver.Types (SourceError, srcErrorMessages, implicitTyThings)
 import GHC.Platform.Host (cHostPlatformMini)
-import GHC.Driver.Types (SourceError, srcErrorMessages)
+import GHC.Tc.Utils.Zonk (hsPatType)
 import GHC.Utils.Error (ErrMsg, pprLocErrMsg)
-import GHC.Data.Bag (Bag)
 
 import Control.Monad (void)
 
@@ -118,5 +181,14 @@
 locA = id
 
 type LOC = Located
+
+guessTarget :: G.GhcMonad m => String -> m G.Target
+guessTarget file = G.guessTarget file Nothing
+
+pprSigmaType :: G.Type -> SDoc
+pprSigmaType = pprTypeForUser
+
+getMessages :: a -> a
+getMessages = id
 ----------------------------------------------------------------
 #endif
diff --git a/lib/Hhp/Info.hs b/lib/Hhp/Info.hs
--- a/lib/Hhp/Info.hs
+++ b/lib/Hhp/Info.hs
@@ -7,7 +7,7 @@
   , types
   ) where
 
-import GHC (Ghc, TypecheckedModule(..), DynFlags, SrcSpan, Type, GenLocated(L), ModSummary, mgModSummaries, mg_ext, LHsBind, Type, LPat, LHsExpr)
+import GHC (Ghc, TypecheckedModule(..), SrcSpan, Type, GenLocated(L), ModSummary, mgModSummaries, mg_ext, LHsBind, Type, LPat, LHsExpr)
 import qualified GHC as G
 import GHC.Core.Type (mkVisFunTys)
 import GHC.Core.Utils (exprType)
@@ -15,9 +15,9 @@
 import GHC.Hs.Expr (MatchGroupTc(..))
 import GHC.Hs.Extension (GhcTc)
 import GHC.HsToCore (deSugarExpr)
-import GHC.Tc.Utils.Zonk (hsPatType)
 import GHC.Utils.Monad (liftIO)
-import GHC.Utils.Outputable (PprStyle)
+import GHC.Utils.Outputable (SDocContext)
+import GHC.Driver.Session (initSDocContext)
 
 import Control.Applicative ((<|>))
 import Control.Monad (filterM)
@@ -54,9 +54,9 @@
      -> Ghc String
 info opt file expr = convert opt <$> handle handler body
   where
-    body = inModuleContext file $ \dflag style -> do
+    body = inModuleContext file $ \ctx -> do
         sdoc <- infoThing expr
-        return $ showPage dflag style sdoc
+        return $ showPage ctx sdoc
     handler (SomeException _e) = return $ "Cannot show info: " ++ show _e
 
 ----------------------------------------------------------------
@@ -80,10 +80,10 @@
       -> Ghc String
 types opt file lineNo colNo = convert opt <$> handle handler body
   where
-    body = inModuleContext file $ \dflag style -> do
+    body = inModuleContext file $ \ctx -> do
         modSum <- fileModSummary file
         srcSpanTypes <- getSrcSpanType modSum lineNo colNo
-        return $ map (toTup dflag style) $ sortBy (cmp `on` fst) srcSpanTypes
+        return $ map (toTup ctx) $ sortBy (cmp `on` fst) srcSpanTypes
     handler (SomeException _) = return []
 
 type LExpression = LHsExpr GhcTc
@@ -108,33 +108,35 @@
   | b `G.isSubspanOf` a = O.GT
   | otherwise           = O.EQ
 
-toTup :: DynFlags -> PprStyle -> (SrcSpan, Type) -> ((Int,Int,Int,Int),String)
-toTup dflag style (spn, typ) = (fourInts spn, pretty dflag style typ)
+toTup :: SDocContext -> (SrcSpan, Type) -> ((Int,Int,Int,Int),String)
+toTup ctx (spn, typ) = (fourInts spn, pretty ctx typ)
 
 fourInts :: SrcSpan -> (Int,Int,Int,Int)
 fourInts = fromMaybe (0,0,0,0) . getSrcSpan
 
-pretty :: DynFlags -> PprStyle -> Type -> String
-pretty dflag style = showOneLine dflag style . pprTypeForUser
+pretty :: SDocContext -> Type -> String
+pretty ctx = showOneLine ctx . pprSigmaType
 
 ----------------------------------------------------------------
 
-inModuleContext :: FilePath -> (DynFlags -> PprStyle -> Ghc a) -> Ghc a
+inModuleContext :: FilePath -> (SDocContext -> Ghc a) -> Ghc a
 inModuleContext file action =
     withDynFlags (setWarnTypedHoles . setDeferTypeErrors . setNoWarningFlags) $ do
     setTargetFiles [file]
     withContext $ do
         dflag <- G.getSessionDynFlags
         style <- getStyle
-        action dflag style
+        action $ initSDocContext dflag style
 
 ----------------------------------------------------------------
 
 fileModSummary :: FilePath -> Ghc ModSummary
 fileModSummary file = do
     mss <- mgModSummaries <$> G.getModuleGraph
-    let [ms] = filter (\m -> G.ml_hs_file (G.ms_location m) == Just file) mss
-    return ms
+    let xs = filter (\m -> G.ml_hs_file (G.ms_location m) == Just file) mss
+    case xs of
+      [ms] -> return ms
+      _    -> error "fileModSummary"
 
 withContext :: Ghc a -> Ghc a
 withContext action = bracket setup teardown body
diff --git a/lib/Hhp/Logger.hs b/lib/Hhp/Logger.hs
--- a/lib/Hhp/Logger.hs
+++ b/lib/Hhp/Logger.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE BangPatterns #-}
 
 module Hhp.Logger (
@@ -10,11 +11,19 @@
 import qualified GHC as G
 import GHC.Data.Bag (bagToList)
 import GHC.Data.FastString (unpackFS)
-import GHC.Driver.Session (dopt, DumpFlag(Opt_D_dump_splices))
-import GHC.Utils.Error (Severity(..), errMsgSpan)
+import GHC.Driver.Session (initSDocContext)
+import GHC.Utils.Error (Severity(..)) -- errMsgSpan
 import GHC.Utils.Monad (liftIO)
-import GHC.Utils.Outputable (PprStyle, SDoc, defaultDumpStyle)
+import GHC.Utils.Outputable (SDoc, SDocContext)
 
+#if __GLASGOW_HASKELL__ >= 904
+import GHC.Utils.Error (MessageClass(..))
+import GHC.Utils.Logger (LogFlags(..))
+#else
+import GHC.Driver.Session (dopt, DumpFlag(Opt_D_dump_splices))
+import Hhp.Doc (styleUnqualified)
+#endif
+
 import Control.Monad.Catch (handle)
 import Data.IORef (IORef, newIORef, readIORef, writeIORef, modifyIORef)
 import Data.List (isPrefixOf)
@@ -28,22 +37,35 @@
 
 ----------------------------------------------------------------
 
-type Builder = [String] -> [String]
+type LogInfo = (Bool,SDocContext,Severity,SrcSpan,SDoc)
 
-newtype LogRef = LogRef (IORef Builder)
+newtype LogRef = LogRef (IORef ([LogInfo] -> [LogInfo]))
 
 newLogRef :: IO LogRef
 newLogRef = LogRef <$> newIORef id
 
 readAndClearLogRef :: Options -> LogRef -> IO String
 readAndClearLogRef opt (LogRef ref) = do
-    b <- readIORef ref
+    build <- readIORef ref
     writeIORef ref id
-    return $! convert opt (b [])
+    let logInfos = build []
+        logmsg = map ppMsg logInfos
+    return $! convert opt logmsg
 
 appendLogRef :: LogRef -> LogAction
-appendLogRef (LogRef ref) df _mc sev src msg = do
-    let !l = ppMsg src sev df msg
+#if __GLASGOW_HASKELL__ >= 904
+appendLogRef (LogRef ref) flag mc src msg = do
+    let (dump,sev) = case mc of
+          MCDiagnostic sev0 _ -> (False, sev0)
+          _                   -> (True,  SevError) -- dummy
+        ctx = log_default_user_context flag
+        !l = (dump, ctx, sev, src, msg)
+#else
+appendLogRef (LogRef ref) flag _ sev src msg = do
+    let ctx = initSDocContext flag styleUnqualified
+        dump = isDumpSplices flag
+        !l = (dump, ctx, sev, src, msg)
+#endif
     modifyIORef ref (\b -> b . (l:))
 
 ----------------------------------------------------------------
@@ -69,36 +91,34 @@
 sourceError opt err = do
     dflag <- G.getSessionDynFlags
     style <- getStyle
-    let ret = convert opt . errBagToStrList dflag style . srcErrorMessages $ err
+    let ctx = initSDocContext dflag style
+        ret = convert opt . errBagToStrList ctx . srcErrorMessages $ err
     return (Left ret)
 
-errBagToStrList :: DynFlags -> PprStyle -> ErrorMessages -> [String]
-errBagToStrList dflag style = map (ppErrMsg style) . reverse . bagToList
+errBagToStrList :: SDocContext -> ErrorMessages -> [String]
+errBagToStrList ctx = map ppErrMsg . reverse . bagToList . getMessages
   where
-    ppErrMsg _style_fixme err = ppMsg spn SevError dflag msg -- ++ ext
+    ppErrMsg err = showPage ctx msg
        where
-         spn = errMsgSpan err
+--         spn = errMsgSpan err
          msg = pprLocErrMessage err
-         -- fixme
-    --     ext = showPage dflag style (pprLocErrMsg $ errMsgReason err)
 
-ppMsg :: SrcSpan -> Severity -> DynFlags -> SDoc -> String
-ppMsg spn sev dflag msg = prefix ++ cts
+ppMsg :: (Bool, SDocContext, Severity, SrcSpan, SDoc) -> String
+ppMsg (True,ctx,_   ,_ ,msg) =           showPage ctx msg
+ppMsg (_,   ctx,sev,spn,msg) = prefix ++ showPage ctx msg
   where
-    cts  = showPage dflag defaultDumpStyle msg
-    defaultPrefix
-      | isDumpSplices dflag = ""
-      | otherwise           = checkErrorPrefix
-    prefix = fromMaybe defaultPrefix $ do
+    prefix = fromMaybe checkErrorPrefix $ do
         (line,col,_,_) <- getSrcSpan spn
         file <- normalise <$> getSrcFile spn
         let severityCaption = showSeverityCaption sev
         return $ file ++ ":" ++ show line ++ ":" ++ show col ++ ":" ++ severityCaption
 
+
 checkErrorPrefix :: String
 checkErrorPrefix = "Dummy:0:0:Error:"
 
 showSeverityCaption :: Severity -> String
+-- showSeverityCaption SevError is not necessary for historical reasons
 showSeverityCaption SevWarning = "Warning: "
 showSeverityCaption _          = ""
 
@@ -106,8 +126,10 @@
 getSrcFile (G.RealSrcSpan spn _) = Just . unpackFS . G.srcSpanFile $ spn
 getSrcFile _                     = Nothing
 
+#if __GLASGOW_HASKELL__ < 904
 isDumpSplices :: DynFlags -> Bool
 isDumpSplices dflag = dopt Opt_D_dump_splices dflag
+#endif
 
 getSrcSpan :: SrcSpan -> Maybe (Int,Int,Int,Int)
 getSrcSpan (RealSrcSpan spn _) = Just ( G.srcSpanStartLine spn
diff --git a/src/hhpi.hs b/src/hhpi.hs
--- a/src/hhpi.hs
+++ b/src/hhpi.hs
@@ -214,7 +214,9 @@
          -> FilePath
          -> Ghc (String, Bool, Set FilePath)
 showInfo opt set fileArg = do
-    let [file, expr] = words fileArg
+    let (file, expr) = case words fileArg of
+          [file0, expr0] -> (file0, expr0)
+          _              -> error "showInfo"
     set' <- newFileSet set file
     ret <- info opt file expr
     return (ret, True, set')
@@ -224,7 +226,9 @@
          -> FilePath
          -> Ghc (String, Bool, Set FilePath)
 showType opt set fileArg  = do
-    let [file, line, column] = words fileArg
+    let (file, line, column) = case words fileArg of
+          [file0, line0, column0] -> (file0, line0, column0)
+          _                       -> error "showInfo"
     set' <- newFileSet set file
     ret <- types opt file (read line) (read column)
     return (ret, True, set')
diff --git a/test/CheckSpec.hs b/test/CheckSpec.hs
--- a/test/CheckSpec.hs
+++ b/test/CheckSpec.hs
@@ -28,7 +28,7 @@
             withDirectory_ "test/data" $ do
                 cradle <- findCradleWithoutSandbox
                 res <- checkSyntax defaultOptions cradle ["Mutual1.hs"]
-                res `shouldSatisfy` ("Module imports form a cycle" `isInfixOf`)
+                res `shouldSatisfy` ("a cycle" `isInfixOf`)
 
         it "can check a module using QuasiQuotes" $ do
             withDirectory_ "test/data" $ do