diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # hs2ats
 
+## 0.5.0.0
+
+  * Re-add `cpphs` dependency
+
 ## 0.4.0.0
   
   * Stop depending on `cpphs`
diff --git a/app/Main.hs b/app/Main.hs
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -12,10 +12,11 @@
 
 data Program = Program { src    :: FilePath <?> "Haskell source file"
                        , target :: FilePath <?> "ATS target"
+                       , cpphs  :: Bool <?> "Use cpphs as a preprocessor"
                        } deriving (Generic, ParseRecord)
 
 main :: IO ()
 main = do
     x <- getRecord "Generate ATS types for Haskell source code" :: IO Program
     let go = (x &) . (unHelpful .)
-    genATSTypes (go src) (go target)
+    genATSTypes (go src) (go target) (go cpphs)
diff --git a/hs2ats.cabal b/hs2ats.cabal
--- a/hs2ats.cabal
+++ b/hs2ats.cabal
@@ -1,6 +1,6 @@
 cabal-version: 1.18
 name: hs2ats
-version: 0.4.0.0
+version: 0.5.0.0
 license: BSD3
 license-file: LICENSE
 copyright: Copyright: (c) 2018 Vanessa McHale
@@ -41,7 +41,8 @@
         microlens -any,
         ansi-wl-pprint -any,
         composition-prelude -any,
-        deepseq -any
+        deepseq -any,
+        cpphs -any
 
     if flag(development)
         ghc-options: -Werror
diff --git a/src/Language/ATS/Generate.hs b/src/Language/ATS/Generate.hs
--- a/src/Language/ATS/Generate.hs
+++ b/src/Language/ATS/Generate.hs
@@ -10,6 +10,7 @@
     ) where
 
 import           Control.Arrow
+import           Data.Bool                    (bool)
 import           Data.Char                    (toUpper)
 import           Data.Either                  (lefts, rights)
 import           Data.Foldable
@@ -19,6 +20,7 @@
 import           Language.ATS.Generate.Error
 import           Language.Haskell.Exts
 import           Language.Haskell.Exts.Syntax as HS
+import           Language.Preprocessor.Cpphs  (defaultCpphsOptions, runCpphs)
 import           Lens.Micro                   (over, _head)
 import           Text.Casing                  (quietSnake)
 
@@ -172,10 +174,15 @@
     ParseOk x            -> Right x
     ParseFailed loc' msg -> syntaxError (loc' { srcFilename = file }) msg
 
+process :: FilePath -> String -> IO String
+process p = fmap (unlines . drop 1 . lines) . runCpphs defaultCpphsOptions p
+
 genATSTypes :: FilePath -- ^ Haskell source file
             -> FilePath -- ^ @.sats@ file to be generated
+            -> Bool -- ^ Whether to use pre-process the Haskell source (use this if you use @{\#- LANGUAGE CPP \#-}@ anywhere)
             -> IO ()
-genATSTypes p p' = do
-    contents <- readFile p
+genATSTypes p p' withCPP = do
+    let proc = bool pure (process p) withCPP
+    contents <- proc =<< readFile p
     let warnDo (x, es) = traverse_ displayErr es *> writeFile p' x
     either displayErr warnDo (generateATS p contents)