diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+# 1.0.0.1
+* Now supports ghc-9.0 (and remains compatible with ghc-8.10)
+
 # 1.0
 * Now supports ghc-8.10! Unfortunately, ghc-8.6 and ghc-8.8 are no longer
   supported.
diff --git a/src/TypeLevel/Rewrite.hs b/src/TypeLevel/Rewrite.hs
--- a/src/TypeLevel/Rewrite.hs
+++ b/src/TypeLevel/Rewrite.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE LambdaCase, OverloadedStrings, RecordWildCards, ViewPatterns #-}
+{-# LANGUAGE CPP, LambdaCase, OverloadedStrings, RecordWildCards, ViewPatterns #-}
 module TypeLevel.Rewrite (plugin) where
 
 import Control.Monad
@@ -8,6 +8,17 @@
 import Data.Traversable
 
 -- GHC API
+#if MIN_VERSION_ghc(9,0,0)
+import GHC.Core.Coercion (Role(Representational), mkUnivCo)
+import GHC.Tc.Types.Constraint (CtEvidence(ctev_loc), Ct, ctEvExpr, ctLoc, mkNonCanonical)
+import GHC.Plugins (PredType, SDoc, eqType, fsep, ppr)
+import GHC.Plugins (Plugin(pluginRecompile, tcPlugin), CommandLineOption, defaultPlugin, purePlugin)
+import GHC.Tc.Types.Evidence (EvExpr, EvTerm, evCast)
+import GHC.Tc.Plugin (newWanted)
+import GHC.Core.TyCo.Rep (UnivCoProvenance(PluginProv))
+import GHC.Plugins (synTyConDefn_maybe)
+import GHC.Tc.Types (TcPluginResult(..), TcPluginM, ErrCtxt, pushErrCtxtSameOrigin, TcPlugin(..))
+#else
 import Coercion (Role(Representational), mkUnivCo)
 import Constraint (CtEvidence(ctev_loc), Ct, ctEvExpr, ctLoc, mkNonCanonical)
 import GhcPlugins (PredType, SDoc, eqType, fsep, ppr)
@@ -17,6 +28,7 @@
 import TcRnTypes
 import TyCoRep (UnivCoProvenance(PluginProv))
 import TyCon (synTyConDefn_maybe)
+#endif
 
 import TypeLevel.Rewrite.Internal.ApplyRules
 import TypeLevel.Rewrite.Internal.DecomposedConstraint
diff --git a/src/TypeLevel/Rewrite/Internal/ApplyRules.hs b/src/TypeLevel/Rewrite/Internal/ApplyRules.hs
--- a/src/TypeLevel/Rewrite/Internal/ApplyRules.hs
+++ b/src/TypeLevel/Rewrite/Internal/ApplyRules.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE LambdaCase, TupleSections, ViewPatterns #-}
+{-# LANGUAGE CPP, LambdaCase, TupleSections, ViewPatterns #-}
 {-# OPTIONS -Wno-name-shadowing #-}
 module TypeLevel.Rewrite.Internal.ApplyRules where
 
@@ -13,7 +13,11 @@
 import qualified Data.Map as Map
 
 -- GHC API
+#if MIN_VERSION_ghc(9,0,0)
+import GHC.Plugins (TyVar)
+#else
 import Type (TyVar)
+#endif
 
 -- term-rewriting API
 import Data.Rewriting.Rule (Rule(..))
diff --git a/src/TypeLevel/Rewrite/Internal/DecomposedConstraint.hs b/src/TypeLevel/Rewrite/Internal/DecomposedConstraint.hs
--- a/src/TypeLevel/Rewrite/Internal/DecomposedConstraint.hs
+++ b/src/TypeLevel/Rewrite/Internal/DecomposedConstraint.hs
@@ -1,12 +1,17 @@
-{-# LANGUAGE DeriveFunctor, DeriveFoldable, DeriveTraversable, LambdaCase, RecordWildCards, ViewPatterns #-}
+{-# LANGUAGE CPP, DeriveFunctor, DeriveFoldable, DeriveTraversable, LambdaCase, RecordWildCards, ViewPatterns #-}
 module TypeLevel.Rewrite.Internal.DecomposedConstraint where
 
 import Control.Applicative
 
 -- GHC API
 import GHC (Class, Type)
+#if MIN_VERSION_ghc(9,0,0)
+import GHC.Tc.Types.Constraint (Ct, ctEvPred, ctEvidence)
+import GHC.Core.Predicate (EqRel(NomEq), Pred(ClassPred, EqPred), classifyPredType, mkClassPred, mkPrimEqPred)
+#else
 import Constraint (Ct, ctEvPred, ctEvidence)
 import Predicate (EqRel(NomEq), Pred(ClassPred, EqPred), classifyPredType, mkClassPred, mkPrimEqPred)
+#endif
 
 
 data DecomposedConstraint a
diff --git a/src/TypeLevel/Rewrite/Internal/Lookup.hs b/src/TypeLevel/Rewrite/Internal/Lookup.hs
--- a/src/TypeLevel/Rewrite/Internal/Lookup.hs
+++ b/src/TypeLevel/Rewrite/Internal/Lookup.hs
@@ -1,21 +1,29 @@
-{-# LANGUAGE LambdaCase, ViewPatterns #-}
+{-# LANGUAGE CPP, LambdaCase, ViewPatterns #-}
 module TypeLevel.Rewrite.Internal.Lookup where
 
 import Control.Arrow ((***), first)
 import Data.Tuple (swap)
 
 -- GHC API
-import Finder (cannotFindModule)
 import GHC (DataCon, TyCon, dataConTyCon)
+#if MIN_VERSION_ghc(9,0,0)
+import GHC.Driver.Finder (cannotFindModule)
+import GHC (Module, ModuleName, mkModuleName)
+import GHC.Plugins (mkDataOcc, mkTcOcc)
+import GHC.Utils.Panic (panicDoc)
+import GHC.Tc.Plugin
+  ( FindResult(Found), TcPluginM, findImportedModule, lookupOrig, tcLookupDataCon, tcLookupTyCon
+  , unsafeTcPluginTcM
+  )
+import GHC.Tc.Solver.Monad (getDynFlags)
+#else
+import Finder (cannotFindModule)
 import Module (Module, ModuleName, mkModuleName)
 import OccName (mkDataOcc, mkTcOcc)
 import Panic (panicDoc)
 import TcPluginM
-  ( FindResult(Found), TcPluginM, findImportedModule, lookupOrig, tcLookupDataCon, tcLookupTyCon
-  , unsafeTcPluginTcM
-  )
 import TcSMonad (getDynFlags)
-
+#endif
 
 lookupModule
   :: String  -- ^ module name
diff --git a/src/TypeLevel/Rewrite/Internal/PrettyPrint.hs b/src/TypeLevel/Rewrite/Internal/PrettyPrint.hs
--- a/src/TypeLevel/Rewrite/Internal/PrettyPrint.hs
+++ b/src/TypeLevel/Rewrite/Internal/PrettyPrint.hs
@@ -1,12 +1,18 @@
-{-# LANGUAGE LambdaCase, RecordWildCards #-}
+{-# LANGUAGE CPP, LambdaCase, RecordWildCards #-}
 module TypeLevel.Rewrite.Internal.PrettyPrint where
 
 import Data.List (intercalate)
 
 -- GHC API
+#if MIN_VERSION_ghc(9,0,0)
+import GHC.Utils.Outputable (ppr, showSDocUnsafe)
+import GHC.Plugins (TyCon)
+import GHC.Plugins (TyVar, Type)
+#else
 import Outputable (ppr, showSDocUnsafe)
 import TyCon (TyCon)
 import Type (TyVar, Type)
+#endif
 
 -- term-rewriting API
 import Data.Rewriting.Rule (Rule(..))
diff --git a/src/TypeLevel/Rewrite/Internal/TypeEq.hs b/src/TypeLevel/Rewrite/Internal/TypeEq.hs
--- a/src/TypeLevel/Rewrite/Internal/TypeEq.hs
+++ b/src/TypeLevel/Rewrite/Internal/TypeEq.hs
@@ -1,8 +1,13 @@
+{-# LANGUAGE CPP #-}
 module TypeLevel.Rewrite.Internal.TypeEq where
 
 import Data.Function
 
+#if MIN_VERSION_ghc(9,0,0)
+import GHC.Plugins (Type, eqType)
+#else
 import GhcPlugins (Type, eqType)
+#endif
 
 
 -- | A newtype around 'Type' which has an 'Eq' instance.
diff --git a/src/TypeLevel/Rewrite/Internal/TypeNode.hs b/src/TypeLevel/Rewrite/Internal/TypeNode.hs
--- a/src/TypeLevel/Rewrite/Internal/TypeNode.hs
+++ b/src/TypeLevel/Rewrite/Internal/TypeNode.hs
@@ -1,9 +1,14 @@
-{-# LANGUAGE ViewPatterns #-}
+{-# LANGUAGE CPP, ViewPatterns #-}
 module TypeLevel.Rewrite.Internal.TypeNode where
 
 -- GHC API
+#if MIN_VERSION_ghc(9,0,0)
+import GHC (TyCon)
+import GHC.Plugins (Type, isNumLitTy, isStrLitTy, mkTyConApp, splitTyConApp_maybe)
+#else
 import TyCon (TyCon)
 import Type (Type, isNumLitTy, isStrLitTy, mkTyConApp, splitTyConApp_maybe)
+#endif
 
 import TypeLevel.Rewrite.Internal.TypeEq
 
diff --git a/src/TypeLevel/Rewrite/Internal/TypeRule.hs b/src/TypeLevel/Rewrite/Internal/TypeRule.hs
--- a/src/TypeLevel/Rewrite/Internal/TypeRule.hs
+++ b/src/TypeLevel/Rewrite/Internal/TypeRule.hs
@@ -1,11 +1,17 @@
-{-# LANGUAGE LambdaCase, ViewPatterns #-}
+{-# LANGUAGE CPP, LambdaCase, ViewPatterns #-}
 {-# OPTIONS -Wno-name-shadowing #-}
 module TypeLevel.Rewrite.Internal.TypeRule where
 
 -- GHC API
+#if MIN_VERSION_ghc(9,0,0)
+import GHC.Plugins (getOccString)
+import GHC.Core.Predicate (mkPrimEqPred)
+import GHC.Plugins (TyVar, Type, mkTyVarTy)
+#else
 import Name (getOccString)
 import Predicate (mkPrimEqPred)
 import Type (TyVar, Type, mkTyVarTy)
+#endif
 
 -- term-rewriting API
 import Data.Rewriting.Rule (Rule(..))
diff --git a/src/TypeLevel/Rewrite/Internal/TypeTemplate.hs b/src/TypeLevel/Rewrite/Internal/TypeTemplate.hs
--- a/src/TypeLevel/Rewrite/Internal/TypeTemplate.hs
+++ b/src/TypeLevel/Rewrite/Internal/TypeTemplate.hs
@@ -1,8 +1,12 @@
-{-# LANGUAGE LambdaCase, ViewPatterns #-}
+{-# LANGUAGE CPP, LambdaCase, ViewPatterns #-}
 module TypeLevel.Rewrite.Internal.TypeTemplate where
 
 -- GHC API
+#if MIN_VERSION_ghc(9,0,0)
+import GHC.Plugins (TyVar, Type, getTyVar_maybe)
+#else
 import Type (TyVar, Type, getTyVar_maybe)
+#endif
 
 -- term-rewriting API
 import Data.Rewriting.Term (Term(Fun, Var))
diff --git a/src/TypeLevel/Rewrite/Internal/TypeTerm.hs b/src/TypeLevel/Rewrite/Internal/TypeTerm.hs
--- a/src/TypeLevel/Rewrite/Internal/TypeTerm.hs
+++ b/src/TypeLevel/Rewrite/Internal/TypeTerm.hs
@@ -1,8 +1,12 @@
-{-# LANGUAGE LambdaCase, ViewPatterns #-}
+{-# LANGUAGE CPP, LambdaCase, ViewPatterns #-}
 module TypeLevel.Rewrite.Internal.TypeTerm where
 
 -- GHC API
+#if MIN_VERSION_ghc(9,0,0)
+import GHC.Plugins (Type, mkTyConApp)
+#else
 import Type (Type, mkTyConApp)
+#endif
 
 -- term-rewriting API
 import Data.Rewriting.Term (Term(Fun, Var))
diff --git a/test/should-compile/GHC/TypeLits/Test.hs b/test/should-compile/GHC/TypeLits/Test.hs
--- a/test/should-compile/GHC/TypeLits/Test.hs
+++ b/test/should-compile/GHC/TypeLits/Test.hs
@@ -17,6 +17,7 @@
        ~ (s1 `AppendSymbol` ("foo" `AppendSymbol` s2))
       => r
        )
-    -> proxy s
+    -> proxy s1
+    -> proxy s2
     -> r
-ex2 r _ = r
+ex2 r _ _ = r
diff --git a/typelevel-rewrite-rules.cabal b/typelevel-rewrite-rules.cabal
--- a/typelevel-rewrite-rules.cabal
+++ b/typelevel-rewrite-rules.cabal
@@ -1,13 +1,13 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.33.0.
+-- This file has been generated from package.yaml by hpack version 0.35.2.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 2673197ba6a9e92128e851017519e221b95a23ca70b1f7b84158feae74eba11b
+-- hash: 228b6969b9e5934cdf11b460c5fa1ee3e3f5e70e3f58d4b5422a80a9676c49b3
 
 name:           typelevel-rewrite-rules
-version:        1.0
+version:        1.0.0.1
 synopsis:       Solve type equalities using custom type-level rewrite rules
 description:    A typechecker plugin which allows the user to specify a set of domain-specific rewrite rules. These get applied whenever the compiler is unable to solve a type equality constraint, in the hope that the rewritten equality constraint will be easier to solve.
 category:       Type System
@@ -17,6 +17,9 @@
 maintainer:     gelisam+github@gmail.com
 license:        PublicDomain
 build-type:     Simple
+tested-with:
+    GHC == 9.0.2
+  , GHC == 8.10.7
 extra-source-files:
     README.md
     CHANGELOG.md
@@ -48,7 +51,7 @@
   build-depends:
       base >=4.12 && <5
     , containers >=0.6.2.1
-    , ghc >=8.10.2 && <9.0
+    , ghc >=8.10.2 && <9.1
     , ghc-prim >=0.5.3
     , term-rewriting >=0.3.0.1
     , transformers >=0.5.6.2