diff --git a/exe/Main.hs b/exe/Main.hs
new file mode 100644
--- /dev/null
+++ b/exe/Main.hs
@@ -0,0 +1,14 @@
+{-# language TemplateHaskell #-}
+module Main where
+
+import Control.Lens
+
+data Person
+  = Person
+  { _name :: String
+  } deriving (Show, Eq)
+
+main :: IO ()
+main = pure ()
+
+$(makeLenses ''Person)
diff --git a/lens-th-rewrite.cabal b/lens-th-rewrite.cabal
--- a/lens-th-rewrite.cabal
+++ b/lens-th-rewrite.cabal
@@ -1,6 +1,6 @@
 cabal-version:       >=1.10
 name:                lens-th-rewrite
-version:             0.1.0.0
+version:             0.3.0.0
 synopsis:            Rewrites Template Haskell splices using the API
 description:         A GHC plugin to perform source-to-source transformation on parsed Haskell, used to manually inline Template Haskell calls for lens.
 bug-reports:         https://github.com/dmjio/lens-th-rewrite/issues
@@ -12,6 +12,28 @@
 category:            Data
 build-type:          Simple
 extra-source-files:  CHANGELOG.md
+
+executable test
+  main-is:
+    Main.hs
+  hs-source-dirs:
+    exe
+  ghc-options:
+    -fplugin=GHC.Plugin.LensThRewrite
+  build-depends:
+    base < 5, lens-th-rewrite, lens
+  default-language:
+    Haskell2010
+
+executable lens-th-rewrite-pp
+  main-is:
+    Main.hs
+  hs-source-dirs:
+    pp
+  build-depends:
+    base < 5, lens-th-rewrite, ghc, ghc-exactprint
+  default-language:
+    Haskell2010
 
 library
   exposed-modules:
diff --git a/pp/Main.hs b/pp/Main.hs
new file mode 100644
--- /dev/null
+++ b/pp/Main.hs
@@ -0,0 +1,35 @@
+module Main where
+
+import System.Environment
+import System.Exit
+import GHC.Plugin.LensThRewrite
+
+import Language.Haskell.GHC.ExactPrint.Parsers
+
+import CoreSyn
+import GhcPlugins
+import HsDecls
+import HsDumpAst
+import HsExtension
+import HsSyn
+import OccName
+import RdrName
+import TcEvidence
+import Var
+
+main :: IO ()
+main = do
+  args <- getArgs
+  case args of
+    original:input:output:_ ->
+      go input output
+
+go :: String -> String -> IO ()
+go input output = do
+  result <- parseModule input
+  case result of
+    Right (_, L _ s) -> do
+      let n = rewriteModule s
+      writeFile output $ showSDocUnsafe (ppr n)
+    Left s -> print s >> exitFailure
+
diff --git a/src/GHC/Plugin/LensThRewrite.hs b/src/GHC/Plugin/LensThRewrite.hs
--- a/src/GHC/Plugin/LensThRewrite.hs
+++ b/src/GHC/Plugin/LensThRewrite.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE RecordWildCards #-}
+{-# LANGUAGE CPP             #-}
 {-# LANGUAGE ViewPatterns    #-}
 {-# LANGUAGE BangPatterns    #-}
 --------------------------------------------------------------------------------
@@ -13,7 +14,7 @@
 -- GHC Plugin to rewrite makeLenses call into pure functions.
 --
 --------------------------------------------------------------------------------
-module GHC.Plugin.LensThRewrite ( plugin ) where
+module GHC.Plugin.LensThRewrite ( plugin, rewriteModule ) where
 
 import Control.Arrow
 import Control.Lens
@@ -31,8 +32,6 @@
 import TcEvidence
 import Var
 
-import System.IO.Unsafe
-
 -- | Lens rewrite plugin.
 plugin :: Plugin
 plugin
@@ -41,14 +40,20 @@
   , pluginRecompile = purePlugin
   }
 
+rewriteModule
+   :: HsModule GhcPs
+   -> HsModule GhcPs
+rewriteModule module'
+  = module' & decls %~ concatMap (modifyDecls module')
+
 rewriteMakeLenses
    :: HsParsedModule
    -> Hsc HsParsedModule
-rewriteMakeLenses parsed = do
---  liftIO $ print "Rewriting makeLenses to use lens"
-  pure $ parsed
-       & moduleDecls
-       %~ concatMap (modifyDecls (parsed ^. (hsMod . located)))
+rewriteMakeLenses parsed
+  = pure
+  $ parsed
+  & moduleDecls
+  %~ concatMap (modifyDecls (parsed ^. (hsMod . located)))
 
 parsedModule :: Lens' HsParsedModule (Located (HsModule GhcPs))
 parsedModule = lens hpm_module $ \r f -> r { hpm_module = f }
@@ -113,14 +118,6 @@
 mkVar :: String -> HsExpr GhcPs
 mkVar x = HsVar NoExt (mkName x)
 
--- | test
--- main :: IO ()
--- main = do
---   Right (_, L _ s) <- parseModule "Main.hs"
---   putStrLn $ showSDocUnsafe (showAstData BlankSrcSpan s)
---   let n = s & decls %~ concatMap (modifyDecls s)
---   putStrLn $ showSDocUnsafe (ppr n)
-
 type FieldName = String
 type TypeName = String
 
@@ -209,7 +206,11 @@
                (hsPar
                  $ hsLam
                  $ matchGroup
+#if MIN_VERSION_base (4,13,0)
                  [ lambdaMatch [ varPat "r", varPat "f" ] $
+#else
+                 [ lambdaMatch [ emptyL (varPat "r"), emptyL (varPat "f") ] $
+#endif
                    grhss
                    [ grhs $ recordUpd (hsVar "r")
                      [ hsRecUpdField fieldName (hsVar "f")