diff --git a/src/Data/Ty.hs b/src/Data/Ty.hs
--- a/src/Data/Ty.hs
+++ b/src/Data/Ty.hs
@@ -1,5 +1,5 @@
 {-# LANGUAGE TypeOperators, TypeFamilies, ScopedTypeVariables #-}
-{-# LANGUAGE GADTs, PatternGuards #-}
+{-# LANGUAGE GADTs, PatternGuards, ConstraintKinds #-}
 {-# LANGUAGE KindSignatures #-} -- AsPairTy
 
 {-# OPTIONS_GHC -Wall #-}
diff --git a/ty.cabal b/ty.cabal
--- a/ty.cabal
+++ b/ty.cabal
@@ -1,5 +1,5 @@
 Name:                ty
-Version:             0.1.5
+Version:             0.1.6
 Synopsis:            Typed type representations and equality proofs
 Category:            Data
 Cabal-Version:       >= 1.6