diff --git a/Data/Nimber.hs b/Data/Nimber.hs
--- a/Data/Nimber.hs
+++ b/Data/Nimber.hs
@@ -56,7 +56,7 @@
 instance Exception NimberException
 
 -- |The type of finite nimbers.
-newtype Nimber = Nimber {fromNimber :: Integer} deriving (Eq, Ord)
+newtype Nimber = Nimber Integer deriving (Eq, Ord)
 
 nimSize :: Nimber -> Int
 nimSize (Nimber a) = bit (intLog2 (integerLog2 a))
@@ -162,3 +162,7 @@
   asinh = throw (Innimerable "asinh")
   atanh = throw (Innimerable "atanh")
   acosh = throw (Innimerable "acosh")
+
+-- |Convert a 'Nimber' to the corresponding natural number.
+fromNimber :: Nimber -> Integer
+fromNimber (Nimber a) = a
diff --git a/nimber.cabal b/nimber.cabal
--- a/nimber.cabal
+++ b/nimber.cabal
@@ -1,5 +1,5 @@
 name:                nimber
-version:             0.1.2
+version:             0.1.3
 synopsis:            Finite nimber arithmetic
 description:
   The finite nimbers, 'Nimber', are a quadratically closed field of
@@ -28,4 +28,4 @@
 source-repository this
   type:                git
   location:            https://github.com/andersk/haskell-nimber
-  tag:                 0.1.2
+  tag:                 0.1.3