diff --git a/hls-fourmolu-plugin.cabal b/hls-fourmolu-plugin.cabal
--- a/hls-fourmolu-plugin.cabal
+++ b/hls-fourmolu-plugin.cabal
@@ -1,6 +1,6 @@
 cabal-version:      2.4
 name:               hls-fourmolu-plugin
-version:            1.0.0.2
+version:            1.0.1.1
 synopsis:           Integration with the Fourmolu code formatter
 description:
   Please see the README on GitHub at <https://github.com/haskell/haskell-language-server#readme>
@@ -19,13 +19,14 @@
 library
   exposed-modules:  Ide.Plugin.Fourmolu
   hs-source-dirs:   src
+  ghc-options:      -Wall
   build-depends:
     , base            >=4.12 && <5
     , filepath
-    , fourmolu        ^>=0.3
+    , fourmolu        ^>=0.3 || ^>=0.4
     , ghc
     , ghc-boot-th
-    , ghcide          >=1.2  && <1.5
+    , ghcide          >=1.2  && <1.6
     , hls-plugin-api  >=1.1  && <1.3
     , lens
     , lsp
@@ -38,7 +39,7 @@
   default-language: Haskell2010
   hs-source-dirs:   test
   main-is:          Main.hs
-  ghc-options:      -threaded -rtsopts -with-rtsopts=-N
+  ghc-options:      -Wall -threaded -rtsopts -with-rtsopts=-N
   build-depends:
     , base
     , filepath
diff --git a/src/Ide/Plugin/Fourmolu.hs b/src/Ide/Plugin/Fourmolu.hs
--- a/src/Ide/Plugin/Fourmolu.hs
+++ b/src/Ide/Plugin/Fourmolu.hs
@@ -8,22 +8,20 @@
     provider,
 ) where
 
-import           Control.Exception           (try)
-import           Control.Lens                ((^.))
+import           Control.Exception               (try)
+import           Control.Lens                    ((^.))
 import           Control.Monad.IO.Class
-import           Data.Bifunctor              (first)
-import qualified Data.Text                   as T
-import           Development.IDE             hiding (pluginHandlers)
-import           Development.IDE.GHC.Compat  (moduleNameString)
-import qualified DynFlags                    as D
-import qualified EnumSet                     as S
-import           GHC.LanguageExtensions.Type (Extension (Cpp))
-import           GhcPlugins                  (HscEnv (hsc_dflags))
-import           Ide.PluginUtils             (makeDiffTextEdit)
+import           Data.Bifunctor                  (first)
+import qualified Data.Text                       as T
+import           Development.IDE                 hiding (pluginHandlers)
+import           Development.IDE.GHC.Compat      as Compat hiding (Cpp)
+import qualified Development.IDE.GHC.Compat.Util as S
+import           GHC.LanguageExtensions.Type     (Extension (Cpp))
+import           Ide.PluginUtils                 (makeDiffTextEdit)
 import           Ide.Types
-import           Language.LSP.Server         hiding (defaultConfig)
+import           Language.LSP.Server             hiding (defaultConfig)
 import           Language.LSP.Types
-import           Language.LSP.Types.Lens
+import           Language.LSP.Types.Lens         (HasTabSize (tabSize))
 import           Ormolu
 import           System.FilePath
 
@@ -71,10 +69,10 @@
             format mempty
         ConfigParseError f (_, err) -> do
             sendNotification SWindowShowMessage $
-              ShowMessageParams
-                  { _xtype = MtError
-                  , _message = errorMessage
-                  }
+                ShowMessageParams
+                    { _xtype = MtError
+                    , _message = errorMessage
+                    }
             return . Left $ responseError errorMessage
           where
             errorMessage = "Failed to load " <> T.pack f <> ": " <> T.pack err
@@ -88,12 +86,12 @@
         FormatRange (Range (Position sl _) (Position el _)) ->
             RegionIndices (Just $ sl + 1) (Just $ el + 1)
 
-convertDynFlags :: D.DynFlags -> IO [DynOption]
+convertDynFlags :: DynFlags -> IO [DynOption]
 convertDynFlags df =
     let pp = ["-pgmF=" <> p | not (null p)]
-        p = D.sPgm_F $ D.settings df
-        pm = map (("-fplugin=" <>) . moduleNameString) $ D.pluginModNames df
-        ex = map showExtension $ S.toList $ D.extensionFlags df
+        p = sPgm_F $ Compat.settings df
+        pm = map (("-fplugin=" <>) . moduleNameString) $ pluginModNames df
+        ex = map showExtension $ S.toList $ extensionFlags df
         showExtension = \case
             Cpp -> "-XCPP"
             x   -> "-X" ++ show x