diff --git a/free-functors.cabal b/free-functors.cabal
--- a/free-functors.cabal
+++ b/free-functors.cabal
@@ -1,6 +1,6 @@
 name:                free-functors
-version:             0.6.4.1
-synopsis:            Provides free functors that are adjoint to functors that forget class constraints.
+version:             0.6.5
+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
                      there were no interesting forgetful functors.
@@ -43,8 +43,8 @@
   build-depends:
     base == 4.8.*,
     template-haskell == 2.10.0.*,
-    constraints >= 0.3.2 && < 0.5,
-    transformers >= 0.2.0.0 && < 0.5,
+    constraints >= 0.6 && < 0.7,
+    transformers >= 0.2.0.0 && < 0.6,
     comonad >= 4.0 && < 4.3,
     void >= 0.4 && < 0.8,
     algebraic-classes == 0.6.*
diff --git a/src/Data/Functor/Free.hs b/src/Data/Functor/Free.hs
--- a/src/Data/Functor/Free.hs
+++ b/src/Data/Functor/Free.hs
@@ -11,6 +11,7 @@
   , DeriveFoldable
   , DeriveTraversable
   , TemplateHaskell
+  , PolyKinds
   #-}
 -----------------------------------------------------------------------------
 -- |
@@ -185,7 +186,7 @@
   where
     freeHeader = return $ ForallT [PlainTV a] []
       (AppT c (AppT (AppT free c) (VarT a)))
-    liftAFreeHeader = return $ ForallT [PlainTV f,PlainTV a] [AppT (ConT ''Applicative) (VarT f)] 
+    liftAFreeHeader = return $ ForallT [PlainTV f,PlainTV a] [AppT (ConT ''Applicative) (VarT f)]
       (AppT c (AppT (AppT (AppT liftAFree c) (VarT f)) (VarT a)))
     showHelperHeader = return $ ForallT [PlainTV a] []
       (AppT c (AppT (AppT showHelper sig) (VarT a)))