diff --git a/free-functors.cabal b/free-functors.cabal
--- a/free-functors.cabal
+++ b/free-functors.cabal
@@ -1,5 +1,5 @@
 name:                free-functors
-version:             1.2
+version:             1.2.1
 synopsis:            Free functors, adjoint to functors that forget class constraints.
 description:         A free functor is a left adjoint to a forgetful functor. It used to be the case
                      that the only category that was easy to work with in Haskell was Hask itself, so
@@ -22,7 +22,7 @@
 
 build-type:          Simple
 cabal-version:       >= 1.10
-tested-with:         GHC==9.0.0.20200925, GHC==8.10.2
+tested-with:         GHC==9.0.0.20200925, GHC==8.10.2, GHC==8.8.4
 
 extra-source-files:
   examples/*.hs
@@ -46,8 +46,8 @@
     Haskell2010
 
   build-depends:
-    base >= 4.14 && < 4.16,
-    template-haskell >= 2.16 && < 2.18,
+    base >= 4.13 && < 4.16,
+    template-haskell >= 2.15 && < 2.18,
     transformers == 0.5.*,
     comonad == 5.*,
     derive-lifted-instances >= 0.2.2 && < 0.3,
diff --git a/src/Data/Functor/Cofree/Internal.hs b/src/Data/Functor/Cofree/Internal.hs
--- a/src/Data/Functor/Cofree/Internal.hs
+++ b/src/Data/Functor/Cofree/Internal.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE
-    GADTs
+    CPP
+  , GADTs
   , PolyKinds
   , RankNTypes
   , ViewPatterns
@@ -15,8 +16,10 @@
   , QuantifiedConstraints
   , MultiParamTypeClasses
   , UndecidableSuperClasses
-  , StandaloneKindSignatures
   #-}
+#if __GLASGOW_HASKELL__ >= 810
+{-# LANGUAGE StandaloneKindSignatures #-}
+#endif
 module Data.Functor.Cofree.Internal where
 
 import Data.Monoid (Ap(..))
@@ -45,5 +48,9 @@
   = deriveInstance (cofreeDeriv ccofree)
       [t| forall a c. (c ~=> $clss, c ($cofree c a)) => $clss ($cofree c a) |]
 
+#if __GLASGOW_HASKELL__ < 810
+type a ~=> b = (forall x. (a :: (k -> Constraint)) x => (b :: (k -> Constraint)) x) :: Constraint
+#else
 type (~=>) :: (k -> Constraint) -> (k -> Constraint) -> Constraint
 type a ~=> b = forall x. a x => b x
+#endif
diff --git a/src/Data/Functor/Free/Internal.hs b/src/Data/Functor/Free/Internal.hs
--- a/src/Data/Functor/Free/Internal.hs
+++ b/src/Data/Functor/Free/Internal.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE
-    GADTs
+    CPP
+  , GADTs
   , PolyKinds
   , RankNTypes
   , ViewPatterns
@@ -15,8 +16,10 @@
   , QuantifiedConstraints
   , MultiParamTypeClasses
   , UndecidableSuperClasses
-  , StandaloneKindSignatures
   #-}
+#if __GLASGOW_HASKELL__ >= 810
+{-# LANGUAGE StandaloneKindSignatures #-}
+#endif
 module Data.Functor.Free.Internal where
 
 import Data.Monoid (Ap(..))
@@ -52,5 +55,9 @@
     , deriveInstance (apDeriv idDeriv) [t| forall f a c. (Applicative f, $clss a) => $clss (Ap f a) |]
     ]
 
+#if __GLASGOW_HASKELL__ < 810
+type a ~=> b = (forall x. (a :: (k -> Constraint)) x => (b :: (k -> Constraint)) x) :: Constraint
+#else
 type (~=>) :: (k -> Constraint) -> (k -> Constraint) -> Constraint
 type a ~=> b = forall x. a x => b x
+#endif