diff --git a/higgledy.cabal b/higgledy.cabal
--- a/higgledy.cabal
+++ b/higgledy.cabal
@@ -1,7 +1,7 @@
 cabal-version:       2.4
 
 name:                higgledy
-version:             0.1.1.1
+version:             0.2.0.0
 synopsis:            Partial types as a type constructor.
 description:         Use the generic representation of an ADT to get a higher-kinded data-style interface automatically.
 homepage:            https://github.com/i-am-tom/higgledy
@@ -25,19 +25,19 @@
                        Data.Generic.HKD.Types
   -- other-modules:
   -- other-extensions:
-  build-depends:       base ^>=4.12
-                     , barbies ^>=1.1.0
-                     , generic-lens ^>=1.1.0
-                     , QuickCheck ^>=2.12.6
+  build-depends:       base ^>= 4.12
+                     , barbies ^>= 1.1.0
+                     , generic-lens ^>= 1.1.0
+                     , QuickCheck ^>= 2.12.6
   hs-source-dirs:      src
   default-language:    Haskell2010
 
 test-suite test
-  build-depends:       base ^>=4.12
-                     , doctest ^>=0.16.0
+  build-depends:       base
+                     , doctest ^>= 0.16.0
                      , higgledy
-                     , hspec ^>=2.6.1
-                     , lens ^>=4.17
+                     , hspec ^>= 2.6.1
+                     , lens ^>= 4.17
                      , QuickCheck ^>= 2.12.6
   main-is:             Main.hs
   type:                exitcode-stdio-1.0
diff --git a/src/Data/Generic/HKD/Types.hs b/src/Data/Generic/HKD/Types.hs
--- a/src/Data/Generic/HKD/Types.hs
+++ b/src/Data/Generic/HKD/Types.hs
@@ -171,7 +171,7 @@
   toTuple   :: HKD structure f -> tuple
   fromTuple :: tuple -> HKD structure f
 
-class Function tuple => GToTuple (rep :: Type -> Type) (tuple :: Type)
+class GToTuple (rep :: Type -> Type) (tuple :: Type)
     | rep -> tuple where
   gfromTuple :: tuple -> rep p
   gtoTuple   :: rep p -> tuple
@@ -186,7 +186,7 @@
   gfromTuple (x, y) = gfromTuple x :*: gfromTuple y
   gtoTuple (x :*: y) = (gtoTuple x, gtoTuple y)
 
-instance Function inner => GToTuple (K1 index inner) inner where
+instance GToTuple (K1 index inner) inner where
   gfromTuple = K1
   gtoTuple = unK1