diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 ## Changelog for Weeder
 
+### [`2.5.0`][v2.5.0] - *2023-01-23*
+ 
+- Weeder has been upgraded to support GHC 9.4 (only). As this changes the
+  format of `.hie` files accepted, this is a major version bump. Thanks to @tfausak!
+
 ### [`2.4.1`][v2.4.1] - *2023-01-05*
 
 - Build with `lens-5.2`
diff --git a/src/Weeder/Main.hs b/src/Weeder/Main.hs
--- a/src/Weeder/Main.hs
+++ b/src/Weeder/Main.hs
@@ -1,7 +1,6 @@
 {-# language ApplicativeDo #-}
 {-# language BlockArguments #-}
 {-# language FlexibleContexts #-}
-{-# language LambdaCase #-}
 {-# language NamedFieldPuns #-}
 {-# language OverloadedStrings #-}
 
@@ -9,16 +8,11 @@
 
 module Weeder.Main ( main, mainWithConfig ) where
 
--- algebraic-graphs
-import Algebra.Graph.Export.Dot ( export, defaultStyleViaShow )
-
 -- base
-import Control.Exception ( evaluate )
 import Control.Monad ( guard, unless, when )
 import Control.Monad.IO.Class ( liftIO )
 import Data.Bool
 import Data.Foldable
-import Data.IORef ( atomicModifyIORef, newIORef, readIORef )
 import Data.List ( isSuffixOf )
 import Data.Version ( showVersion )
 import System.Exit ( exitFailure )
@@ -40,13 +34,12 @@
 import System.FilePath ( isExtensionOf )
 
 -- ghc
-import GHC.Iface.Ext.Binary ( HieFileResult( HieFileResult, hie_file_result ), NameCacheUpdater( NCU ), readHieFileWithVersion )
+import GHC.Iface.Ext.Binary ( HieFileResult( HieFileResult, hie_file_result ), readHieFileWithVersion )
 import GHC.Iface.Ext.Types ( HieFile( hie_hs_file ), hieVersion )
 import GHC.Unit.Module ( moduleName, moduleNameString )
 import GHC.Types.Name.Cache ( initNameCache, NameCache )
 import GHC.Types.Name ( occNameString )
 import GHC.Types.SrcLoc ( RealSrcLoc, realSrcSpanStart, srcLocLine )
-import GHC.Types.Unique.Supply ( mkSplitUniqSupply )
 
 -- regex-tdfa
 import Text.Regex.TDFA ( (=~) )
@@ -124,13 +117,13 @@
       then getFilesIn ".hs" "./."
       else pure []
 
-  nameCacheUpdater <-
-    mkNameCacheUpdater
+  nameCache <-
+    initNameCache 'z' []
 
   analysis <-
     flip execStateT emptyAnalysis do
       for_ hieFilePaths \hieFilePath -> do
-        hieFileResult <- liftIO ( readCompatibleHieFileOrExit nameCacheUpdater hieFilePath )
+        hieFileResult <- liftIO ( readCompatibleHieFileOrExit nameCache hieFilePath )
         let hsFileExists = any ( hie_hs_file hieFileResult `isSuffixOf` ) hsFilePaths
         when (requireHsFiles ==> hsFileExists) do
           analyseHieFile hieFileResult
@@ -220,9 +213,9 @@
 
 
 -- | Read a .hie file, exiting if it's an incompatible version.
-readCompatibleHieFileOrExit :: NameCacheUpdater -> FilePath -> IO HieFile
-readCompatibleHieFileOrExit nameCacheUpdater path = do
-  res <- readHieFileWithVersion (\(v, _) -> v == hieVersion) nameCacheUpdater path
+readCompatibleHieFileOrExit :: NameCache -> FilePath -> IO HieFile
+readCompatibleHieFileOrExit nameCache path = do
+  res <- readHieFileWithVersion (\(v, _) -> v == hieVersion) nameCache path
   case res of
     Right HieFileResult{ hie_file_result } ->
       return hie_file_result
@@ -237,20 +230,6 @@
       exitFailure
 
 
-mkNameCacheUpdater :: IO NameCacheUpdater
-mkNameCacheUpdater = do
-  nameCache <- do
-    uniqSupply <- mkSplitUniqSupply 'z'
-    return ( initNameCache uniqSupply [] )
-
-  nameCacheRef <- newIORef nameCache
-
-  let update_nc f = do r <- atomicModifyIORef nameCacheRef f
-                       _ <- evaluate =<< readIORef nameCacheRef
-                       return r
-  return (NCU update_nc)
-
-
 infixr 5 ==>
 
 
@@ -258,4 +237,3 @@
 (==>) :: Bool -> Bool -> Bool
 True  ==> x = x
 False ==> _ = True
-
diff --git a/weeder.cabal b/weeder.cabal
--- a/weeder.cabal
+++ b/weeder.cabal
@@ -5,7 +5,7 @@
 author:        Ollie Charles <ollie@ocharles.org.uk>
 maintainer:    Ollie Charles <ollie@ocharles.org.uk>
 build-type:    Simple
-version:       2.4.1
+version:       2.5.0
 copyright:     Neil Mitchell 2017-2020, Oliver Charles 2020-2023
 synopsis:      Detect dead code
 description:   Find declarations.
@@ -19,19 +19,19 @@
 library
   build-depends:
     , algebraic-graphs     ^>= 0.4 || ^>= 0.5  || ^>= 0.6
-    , base                 ^>= 4.16.0.0
+    , base                 ^>= 4.17.0.0
     , bytestring           ^>= 0.10.9.0 || ^>= 0.11.0.0
     , containers           ^>= 0.6.2.1
     , dhall                ^>= 1.30.0 || ^>= 1.31.0 || ^>= 1.32.0 || ^>= 1.33.0 || ^>= 1.34.0 || ^>= 1.35.0 || ^>= 1.36.0 || ^>= 1.37.0 || ^>= 1.40.0 || ^>= 1.41
     , directory            ^>= 1.3.3.2
     , filepath             ^>= 1.4.2.1
     , generic-lens         ^>= 2.2.0.0
-    , ghc                  ^>= 9.2
+    , ghc                  ^>= 9.4
     , lens                 ^>= 5.1 || ^>= 5.2
     , mtl                  ^>= 2.2.2
     , optparse-applicative ^>= 0.14.3.0 || ^>= 0.15.1.0 || ^>= 0.16.0.0 || ^>=  0.17
     , regex-tdfa           ^>= 1.2.0.0 || ^>= 1.3.1.0
-    , text                 ^>= 1.2.3.0
+    , text                 ^>= 2.0.1
     , transformers         ^>= 0.5.6.2 || ^>= 0.6
   hs-source-dirs: src
   exposed-modules: