diff --git a/src/TypeUnary/Nat.hs b/src/TypeUnary/Nat.hs
--- a/src/TypeUnary/Nat.hs
+++ b/src/TypeUnary/Nat.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE TypeOperators, GADTs, KindSignatures, RankNTypes #-}
+{-# LANGUAGE FlexibleContexts #-}
 {-# OPTIONS_GHC -Wall #-}
 ----------------------------------------------------------------------
 -- |
diff --git a/type-unary.cabal b/type-unary.cabal
--- a/type-unary.cabal
+++ b/type-unary.cabal
@@ -1,5 +1,5 @@
 Name:                type-unary
-Version:             0.1.11
+Version:             0.1.12
 Cabal-Version:       >= 1.2
 Synopsis:            
   Type-level and typed unary natural numbers, inequality proofs, vectors