diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -3,7 +3,6 @@
 **Delete half (minus ε) of your Haskell code!**
 
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-[![Hackage](http://img.shields.io/hackage/v/dualizer.svg)](http://hackage.haskell.org/package/dualizer)
 
 Dualizer allows you to eliminate the dual of all your code. Rather than implementing, say, `Comonad` directly, you can define it in terms of its dual – `Monad`:
 
diff --git a/dualizer.cabal b/dualizer.cabal
--- a/dualizer.cabal
+++ b/dualizer.cabal
@@ -1,5 +1,5 @@
 name:               dualizer
-version:            0.1.0.0
+version:            0.1.0.1
 synopsis:           Automatically generate dual constructions.
 description:        A library for defining duals automatically, as well as
                     labeling duals in existing packages.
diff --git a/src/Categorical/Dual.hs b/src/Categorical/Dual.hs
--- a/src/Categorical/Dual.hs
+++ b/src/Categorical/Dual.hs
@@ -16,7 +16,6 @@
 
   , makeDualClass
   , makeDualDec
-  -- , withDual
 
   , labelDual
   , labelSelfDual
@@ -35,6 +34,7 @@
 import           Data.Map (Map)
 import           Data.Maybe
 import           Data.Monoid
+import           Data.Semigroup
 import           Data.Tuple
 import           Data.Void
 import           Language.Haskell.TH
@@ -48,13 +48,16 @@
 
 makeLenses ''DualMappings
 
-instance Monoid DualMappings where
-  mempty = DualMappings Map.empty Map.empty
-  mappend (DualMappings t v) (DualMappings t' v') =
+instance Semigroup DualMappings where
+  DualMappings t v <> DualMappings t' v' =
     -- NB: I reversed the order here, because I _think_ this is supposed to be
     --     right-biased?
-    DualMappings (t' `Map.union` t) (v' `Map.union` v)
+    DualMappings (Map.union t' t) (Map.union v' v)
 
+instance Monoid DualMappings where
+  mempty = DualMappings mempty mempty
+  mappend = (Data.Semigroup.<>)
+
 -- | The empty set of duals, should only be used to initalize the duals for
 --   `Prelude`.
 emptyDuals :: Q DualMappings
@@ -62,11 +65,12 @@
 
 reifyDuals :: DualMappings -> Q Exp
 reifyDuals duals =
-  [e|maybe $(liftData duals) ($(liftData duals) <>) <$> getQ|]
+  [e|maybe $(liftData duals) (mappend $(liftData duals)) <$> getQ|]
 
 shareDuals :: DualMappings -> Q Exp
 shareDuals duals =
-  [e|pure [] <* (putQ . maybe $(liftData duals) ($(liftData duals) <>) =<< getQ)|]
+  [e|pure []
+     <* (putQ . maybe $(liftData duals) (mappend $(liftData duals)) =<< getQ)|]
 
 -- TODO: Move this somewhere better
 data AndMaybe a b = Only a | Indeed a b deriving (Eq, Show)
@@ -360,7 +364,7 @@
 importDuals duals = do
   oldDuals <- getQ
   newDuals <- duals
-  putQ $ maybe newDuals (newDuals <>) oldDuals
+  putQ $ maybe newDuals (mappend newDuals) oldDuals
   pure []
 
 errorNewName :: Name -> Q a
@@ -444,35 +448,3 @@
   let coname = mkName co
   db <- retrieveDuals
   fmap join . traverse (dualizeDec db coname) =<< decs
-
--- | Handles dualizing declarations that don’t introduce a new name. This
---   applies the equivalent declaration to the (already created) dual.
--- withDual :: Q Dec -> Q [Dec]
--- withDual dec =
---   dec >>= (\d ->
---             (\c -> [d, c])
---             <$> case d of
---               FunD n _ -> errorNewName n
---               ValD (VarP n) _ _ -> errorNewName n
---               ValD _ _ _ -> fail "declaration introduces new names"
---               DataD _ n _ _ _ _ -> errorNewName n
---               NewtypeD _ n _ _ _ _ -> errorNewName n
---               TySynD n _ _ -> errorNewName n
---               ClassD _ n _ _ _ -> errorNewName n
---               InstanceD o c t ds -> undefined
---               SigD n _ -> errorNewName n
---               ForeignD f -> undefined
---               InfixD f n -> InfixD f <$> dualName n
---               PragmaD p -> undefined
---               DataFamilyD n _ _ -> errorNewName n
---               DataInstD c n ts k cs dcs -> undefined
---               NewtypeInstD c n ts k c' dcs -> undefined
---               TySynInstD n tse -> undefined
---               OpenTypeFamilyD (TypeFamilyHead n _ _ _) -> errorNewName n
---               ClosedTypeFamilyD (TypeFamilyHead n _ _ _) _ -> errorNewName n
---               RoleAnnotD _ _ -> undefined -- ???
---               StandaloneDerivD ds c -> undefined
---               DefaultSigD n t -> undefined -- ???
---               -- PatSynD n _ _ _ -> errorNewName n
---               -- PatSynSigD n _ _ _ -> errorNewName n
---           )
diff --git a/src/Categorical/Dual/Example.hs b/src/Categorical/Dual/Example.hs
--- a/src/Categorical/Dual/Example.hs
+++ b/src/Categorical/Dual/Example.hs
@@ -142,14 +142,6 @@
   [d| cata :: Functor f => (f a -> a) -> Fix f -> a
       cata f = f . fmap (cata f) . unfix |]
   "ana"
--- withDual [d| infix 3 `cata` |]
-
--- -- | Where do these docs wind up?
--- makeDualDec [d| toMaybe :: forall a. [a] -> Maybe a |] "toList"
--- toMaybe (x : _) = Just x
--- toMaybe []       = Nothing
--- toList (Just x) = [x]
--- toList Nothing  = []
 
 -- | Duals for this module.
 exportDuals "exampleDuals"