diff --git a/Data/Vector/Fixed/Internal/Arity.hs b/Data/Vector/Fixed/Internal/Arity.hs
--- a/Data/Vector/Fixed/Internal/Arity.hs
+++ b/Data/Vector/Fixed/Internal/Arity.hs
@@ -2,6 +2,7 @@
 {-# LANGUAGE TypeFamilies          #-}
 {-# LANGUAGE Rank2Types            #-}
 {-# LANGUAGE ScopedTypeVariables   #-}
+{-# LANGUAGE DeriveDataTypeable    #-}
 -- |
 -- Type class for working with N-ary functions
 module Data.Vector.Fixed.Internal.Arity (
@@ -23,14 +24,18 @@
   , applyM
   ) where
 
+import Data.Typeable (Typeable)
+
+
+
 ----------------------------------------------------------------
 -- Naturals
 ----------------------------------------------------------------
 
 -- | Type level zero
-data Z
+data Z   deriving Typeable
 -- | Successor of n
-data S n
+data S n deriving Typeable
 
 type N1 = S Z
 type N2 = S N1
diff --git a/fixed-vector.cabal b/fixed-vector.cabal
--- a/fixed-vector.cabal
+++ b/fixed-vector.cabal
@@ -1,5 +1,5 @@
 Name:           fixed-vector
-Version:        0.4.2.0
+Version:        0.4.3.0
 Synopsis:       Generic vectors with statically known size.
 Description:
   Generic library for vectors with statically known
@@ -44,6 +44,10 @@
   .
   [@Data.Vector.Fixed.Monomorphic@]
   Wrappers for monomorphic vectors
+  .
+  Changes in 0.4.3.0
+  .
+  * Typeable instance for @S@ and @Z@ added.
   .
   Changes in 0.4.2.0
   .