diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# v0.7.0
+
+ * Support for GHC 9
+
 # v0.6.0
 
  * Support for Elm 0.19 
diff --git a/elm-bridge.cabal b/elm-bridge.cabal
--- a/elm-bridge.cabal
+++ b/elm-bridge.cabal
@@ -1,5 +1,5 @@
 name:                elm-bridge
-version:             0.6.1
+version:             0.7.0
 synopsis:            Derive Elm types and Json code from Haskell types, using aeson's options
 description:         Building the bridge from Haskell to Elm and back. Define types once,
                      and derive the aeson and elm functions at the same time, using any aeson
@@ -13,7 +13,7 @@
 category:            Web, Compiler, Language
 build-type:          Simple
 cabal-version:       >=1.10
-tested-with: GHC==8.4.1, GHC==8.2.2, GHC==8.0.2
+tested-with:         GHC==9.0.1
 
 extra-source-files:
     README.md
@@ -32,7 +32,7 @@
                        Elm.TyRep
                        Elm.Versions
   other-modules:       Elm.Utils
-  build-depends:       base >= 4.9 && < 5,
+  build-depends:       base >= 4.15 && < 5,
                        template-haskell,
                        aeson  >= 1
   default-language:    Haskell2010
diff --git a/src/Elm/Derive.hs b/src/Elm/Derive.hs
--- a/src/Elm/Derive.hs
+++ b/src/Elm/Derive.hs
@@ -94,7 +94,7 @@
         TaggedObject tn cn    -> [|SumEncoding' (TaggedObject tn cn)|]
         UntaggedValue         -> [|SumEncoding' UntaggedValue|]
 
-runDerive :: Name -> [TyVarBndr] -> (Q Exp -> Q Exp) -> Q [Dec]
+runDerive :: Name -> [TyVarBndr ()] -> (Q Exp -> Q Exp) -> Q [Dec]
 runDerive name vars mkBody =
     liftM (:[]) elmDefInst
     where
@@ -122,10 +122,10 @@
       argNames =
           flip map vars $ \v ->
               case v of
-                PlainTV tv    -> tv
-                KindedTV tv _ -> tv
+                PlainTV tv _  -> tv
+                KindedTV tv _ _ -> tv
 
-deriveAlias :: Bool -> A.Options -> Name -> [TyVarBndr] -> [VarStrictType] -> Q [Dec]
+deriveAlias :: Bool -> A.Options -> Name -> [TyVarBndr ()] -> [VarStrictType] -> Q [Dec]
 deriveAlias isNewtype opts name vars conFields =
         runDerive name vars $ \typeName ->
                 [|ETypeAlias (EAlias $typeName $fields omitNothing isNewtype unwrapUnary)|] -- default to no newtype
@@ -140,7 +140,7 @@
             fldName = A.fieldLabelModifier opts $ nameBase fname
             fldType = compileType ftype
 
-deriveSum :: A.Options -> Name -> [TyVarBndr] -> [Con] -> Q [Dec]
+deriveSum :: A.Options -> Name -> [TyVarBndr ()] -> [Con] -> Q [Dec]
 deriveSum opts name vars constrs =
     runDerive name vars $ \typeName ->
         [|ETypeSum (ESum $typeName $sumOpts $sumEncOpts omitNothing allNullary)|]
@@ -164,7 +164,7 @@
                 in [|STC b n (Named $tyArgs)|]
             _ -> fail ("Can't derive this sum: " ++ show c)
 
-deriveSynonym :: A.Options -> Name -> [TyVarBndr] -> Type -> Q [Dec]
+deriveSynonym :: A.Options -> Name -> [TyVarBndr ()] -> Type -> Q [Dec]
 deriveSynonym _ name vars otherT =
     runDerive name vars $ \typeName ->
         [|ETypePrimAlias (EPrimAlias $typeName $otherType)|]
diff --git a/src/Elm/TyRep.hs b/src/Elm/TyRep.hs
--- a/src/Elm/TyRep.hs
+++ b/src/Elm/TyRep.hs
@@ -10,7 +10,6 @@
 
 import           Data.Aeson.Types (SumEncoding (..))
 import           Data.Maybe       (fromMaybe)
-import           Data.Monoid      ((<>))
 
 -- | Type definition, including constructors.
 data ETypeDef