diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -4,6 +4,10 @@
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to the [Haskell Package Versioning Policy](https://pvp.haskell.org/).
 
+## Unreleased
+### [0.7] - 2022-07-01
+- make `Refined` predicate type `p` kind polymorphic (`p :: Type` -> `p :: k`)
+
 ## [0.6.3] - 2022-01-14
 ### Added
 - `Hashable` instance for `Refined`
diff --git a/refined.cabal b/refined.cabal
--- a/refined.cabal
+++ b/refined.cabal
@@ -3,7 +3,7 @@
 name:
   refined
 version:
-  0.6.3
+  0.7
 synopsis:
   Refinement types with static and runtime checking
 description:
diff --git a/src/Refined.hs b/src/Refined.hs
--- a/src/Refined.hs
+++ b/src/Refined.hs
@@ -45,6 +45,7 @@
 {-# LANGUAGE MultiParamTypeClasses      #-}
 {-# LANGUAGE OverloadedStrings          #-}
 {-# LANGUAGE PackageImports             #-}
+{-# LANGUAGE PolyKinds                  #-}
 {-# LANGUAGE RoleAnnotations            #-}
 {-# LANGUAGE ScopedTypeVariables        #-}
 {-# LANGUAGE TemplateHaskell            #-}
@@ -567,7 +568,7 @@
     )
 
 -- | @since 0.1.0.0
-instance (Predicate p x, Typeable p) => Predicate (Not p) x where
+instance (Predicate (p :: k) x, Typeable p, Typeable k) => Predicate (Not p) x where
   validate p x = do
     maybe (Just (RefineNotException (typeRep p)))
           (const Nothing)
@@ -598,7 +599,7 @@
 type (&&) = And
 
 -- | @since 0.1.0.0
-instance ( Predicate l x, Predicate r x, Typeable l, Typeable r
+instance ( Predicate (l :: k) x, Predicate (r :: k) x, Typeable l, Typeable r, Typeable k
          ) => Predicate (And l r) x where
   validate p x = do
     let a = validate @l undefined x
@@ -638,7 +639,7 @@
 type (||) = Or
 
 -- | @since 0.2.0.0
-instance ( Predicate l x, Predicate r x, Typeable l, Typeable r
+instance ( Predicate (l :: k) x, Predicate (r :: k) x, Typeable l, Typeable r, Typeable k
          ) => Predicate (Or l r) x where
   validate p x = do
     let left  = validate @l undefined x
@@ -675,7 +676,7 @@
 -- type (^) = Xor
 
 -- | @since 0.5
-instance ( Predicate l x, Predicate r x, Typeable l, Typeable r
+instance ( Predicate (l :: k) x, Predicate (r :: k) x, Typeable l, Typeable r, Typeable k
          ) => Predicate (Xor l r) x where
   validate p x = do
     let left = validate @l undefined x
@@ -1277,7 +1278,7 @@
 --   @since 0.2.0.0
 type NonZero = NotEqualTo 0
 
--- | A 'Predicate' ensuring that the type is non-empty.
+-- | A 'Predicate' ensuring that the type is empty.
 --
 --   @since 0.5
 type Empty = SizeEqualTo 0
@@ -1292,7 +1293,7 @@
 -- | A typeclass containing "safe" conversions between refined
 --   predicates where the target is /weaker/ than the source:
 --   that is, all values that satisfy the first predicate will
---   be guaranteed to satisy the second.
+--   be guaranteed to satisfy the second.
 --
 --   Take care: writing an instance declaration for your custom
 --   predicates is the same as an assertion that 'weaken' is
diff --git a/src/Refined/Unsafe.hs b/src/Refined/Unsafe.hs
--- a/src/Refined/Unsafe.hs
+++ b/src/Refined/Unsafe.hs
@@ -29,6 +29,7 @@
 
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE PolyKinds #-}
 #if __GLASGOW_HASKELL__ >= 805
 {-# LANGUAGE QuantifiedConstraints #-}
 {-# LANGUAGE RankNTypes #-}
diff --git a/src/Refined/Unsafe/Type.hs b/src/Refined/Unsafe/Type.hs
--- a/src/Refined/Unsafe/Type.hs
+++ b/src/Refined/Unsafe/Type.hs
@@ -31,6 +31,7 @@
 {-# LANGUAGE DeriveFoldable             #-}
 {-# LANGUAGE DerivingStrategies         #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE PolyKinds                  #-}
 {-# LANGUAGE RoleAnnotations            #-}
 {-# LANGUAGE TemplateHaskell            #-}
 
@@ -54,7 +55,7 @@
 -- | A refinement type, which wraps a value of type @x@.
 --
 --   @since 0.1.0.0
-newtype Refined p x
+newtype Refined (p :: k) x
   = Refined x -- ^ @since 0.1.0.0
   deriving newtype
     ( Eq -- ^ @since 0.1.0.0