diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changelog for the [`ghc-typelits-natnormalise`](http://hackage.haskell.org/package/ghc-typelits-natnormalise) package
 
+## 0.1.2 *April 21st 2015*
+* Don't simply expressions with negative exponents
+
 ## 0.1.1 *April 17th 2015*
 * Add workaround for https://ghc.haskell.org/trac/ghc/ticket/10301
 
diff --git a/ghc-typelits-natnormalise.cabal b/ghc-typelits-natnormalise.cabal
--- a/ghc-typelits-natnormalise.cabal
+++ b/ghc-typelits-natnormalise.cabal
@@ -1,5 +1,5 @@
 name:                ghc-typelits-natnormalise
-version:             0.1.1
+version:             0.1.2
 synopsis:            GHC typechecker plugin for types of kind GHC.TypeLits.Nat
 description:
   A type checker plugin for GHC that can solve /equalities/ of types of kind
diff --git a/src/GHC/TypeLits/Normalise/SOP.hs b/src/GHC/TypeLits/Normalise/SOP.hs
--- a/src/GHC/TypeLits/Normalise/SOP.hs
+++ b/src/GHC/TypeLits/Normalise/SOP.hs
@@ -143,7 +143,8 @@
 reduceExp :: (Ord v, Ord c) => Symbol v c -> Symbol v c
 reduceExp (E _                 (P [(I 0)])) = I 1        -- x^0 ==> 1
 reduceExp (E (S [P [I 0]])     _          ) = I 0        -- 0^x ==> 0
-reduceExp (E (S [P [(I i)]])   (P [(I j)])) = I (i ^ j)  -- 2^3 ==> 8
+reduceExp (E (S [P [(I i)]])   (P [(I j)]))
+  | j >= 0                                  = I (i ^ j)  -- 2^3 ==> 8
 
 -- (k ^ i) ^ j ==> k ^ (i * j)
 reduceExp (E (S [P [(E k i)]]) j) = case normaliseExp k (S [e]) of