diff --git a/src/Data/IsTy.hs b/src/Data/IsTy.hs
--- a/src/Data/IsTy.hs
+++ b/src/Data/IsTy.hs
@@ -14,7 +14,7 @@
 -- Type class for typed type representations
 ----------------------------------------------------------------------
 
-module Data.IsTy (IsTy(..),IsTy2(..)) where
+module Data.IsTy (IsTy(..),IsTy2(..),Yes,Yes2) where
 
 import GHC.Prim (Constraint)
 
diff --git a/src/Data/Ty.hs b/src/Data/Ty.hs
--- a/src/Data/Ty.hs
+++ b/src/Data/Ty.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE TypeOperators, ScopedTypeVariables #-}
+{-# LANGUAGE TypeOperators, TypeFamilies, ScopedTypeVariables #-}
 {-# LANGUAGE GADTs, PatternGuards #-}
 {-# LANGUAGE KindSignatures #-} -- AsPairTy
 
@@ -35,6 +35,7 @@
 instance Show (Ty a) where show = show . tyRep
 
 instance IsTy Ty where
+  type IsTyConstraint Ty z = Yes Ty z
   Ty a `tyEq` Ty b | a == b    = unsafeCoerce (Just Refl)
                    | otherwise = Nothing
 
diff --git a/ty.cabal b/ty.cabal
--- a/ty.cabal
+++ b/ty.cabal
@@ -1,5 +1,5 @@
 Name:                ty
-Version:             0.1.4
+Version:             0.1.5
 Synopsis:            Typed type representations and equality proofs
 Category:            Data
 Cabal-Version:       >= 1.6