diff --git a/shake-ext.cabal b/shake-ext.cabal
--- a/shake-ext.cabal
+++ b/shake-ext.cabal
@@ -1,5 +1,5 @@
 name:                shake-ext
-version:             0.4.2.0
+version:             0.5.0.0
 synopsis:            Helper functions for linting with shake 
 description:         This package provides several linters out of the box, as well as functionality for building ATS source files with [shake](http://shakebuild.com/).
 homepage:            https://hub.darcs.net/vmchale/shake-ext
diff --git a/src/Development/Shake/ATS.hs b/src/Development/Shake/ATS.hs
--- a/src/Development/Shake/ATS.hs
+++ b/src/Development/Shake/ATS.hs
@@ -1,10 +1,16 @@
-{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE ScopedTypeVariables  #-}
+{-# LANGUAGE TypeSynonymInstances #-}
 
-module Development.Shake.ATS ( cgen
+module Development.Shake.ATS ( -- * Shake Rules
+                               cgen
                              , cgenPretty
                              , cleanATS
                              , atsBin
+                             -- * Actions
                              , patsHome
+                             -- Types
+                             , Version (..)
                              ) where
 
 import           Control.Monad              (filterM, forM_)
@@ -17,30 +23,38 @@
 import           System.Directory           (copyFile)
 import           System.Exit                (ExitCode (ExitSuccess))
 
+newtype Version = Version [Integer]
+
+instance Show Version where
+    show (Version [])     = ""
+    show (Version [x])    = show x
+    show (Version (x:xs)) = show x ++ "." ++ show (Version xs)
+
 patsHome :: Action String
 patsHome = fromMaybe "/usr/local/lib/ats2-postiats-0.3.8" <$> mh
     where mh = fmap (++ "/.atspkg/compiler/") <$> getEnv "HOME"
 
 -- TODO install the whole compiler?
-atsCommand :: CmdResult r => String -> String -> Action r
-atsCommand sourceFile out = do
-    let home = "/usr/local/lib/ats2-postiats-0.3.8"
+atsCommand :: CmdResult r => Version -> String -> String -> Action r
+atsCommand version sourceFile out = do
+    let home = "/usr/local/lib/ats2-postiats-" ++ show version
     let atsArgs = [EchoStderr False, AddEnv "PATSHOME" home]
-        patsc = "patsopt" -- home ++ "/bin/patsopt"
+        patsc = "patsopt"
     command atsArgs patsc ["--output", out, "-dd", sourceFile, "-cc"]
 
 gcFlag :: Bool -> String
 gcFlag False = "-DATS_MEMALLOC_LIBC"
 gcFlag True  = "-DATS_MEMALLOC_GCBDW"
 
-atsBin :: Bool -> [String] -> String -> String -> Rules ()
-atsBin gc libs sourceFile out =
+-- TODO musl?
+atsBin :: Version -> Bool -> [String] -> String -> String -> Rules ()
+atsBin v gc libs sourceFile out =
     out %> \_ -> do
         need [sourceFile]
-        let home = "/usr/local/lib/ats2-postiats-0.3.8"
+        let home = "/usr/local/lib/ats2-postiats-" ++ show v
         cmd_ ["mkdir", "-p", dropDirectory1 out]
         let toLibs = fmap ("-l" <>)
-        command [EchoStderr False, AddEnv "PATSHOME" home] "patscc" ([sourceFile, "-atsccomp", "gcc -flto -I/usr/local/lib/ats2-postiats-0.3.8/ccomp/runtime/ -I/usr/local/lib/ats2-postiats-0.3.8/", gcFlag gc, "-o", out, "-cleanaft", "-O2", "-mtune=native"] <> toLibs libs)
+        command [EchoStderr False, AddEnv "PATSHOME" home] "patscc" ([sourceFile, "-atsccomp", "gcc -flto -I/usr/local/lib/ats2-postiats-0.3.8/ccomp/runtime/ -I/usr/local/lib/ats2-postiats-0.3.8/", gcFlag gc, "-o", out, "-cleanaft", "-O2", "-mtune=native", "-flto"] <> toLibs libs)
 
 cleanATS :: Rules ()
 cleanATS =
@@ -53,15 +67,15 @@
 
 -- | This provides rules for generating C code from ATS source files in the
 -- @ats-src@ directory.
-cgen :: FilePath -> Rules ()
-cgen dir = do
+cgen :: Version -> FilePath -> Rules ()
+cgen version dir = do
 
     atsDeps
 
     "//*.c" %> \out -> do
         let sourceFile = dir ++ "/" ++ (dropDirectory1 out -<.> "dats")
         need [sourceFile]
-        atsCommand sourceFile out
+        atsCommand version sourceFile out
 
 atsDeps :: Rules ()
 atsDeps =
@@ -76,8 +90,8 @@
             liftIO $ copyFile dep (home ++ "/" ++ dep)
 
 -- | This uses @pats-filter@ to prettify the errors.
-cgenPretty :: Rules ()
-cgenPretty = do
+cgenPretty :: Version -> Rules ()
+cgenPretty version = do
 
     atsDeps
 
@@ -85,7 +99,7 @@
 
         let sourceFile = "ats-src/" ++ (dropDirectory1 out -<.> "dats")
         need [sourceFile]
-        (Exit c, Stderr err) :: (Exit, Stderr String) <- atsCommand sourceFile out
+        (Exit c, Stderr err) :: (Exit, Stderr String) <- atsCommand version sourceFile out
         cmd_ [Stdin err] Shell "pats-filter"
         if c /= ExitSuccess
             then error "patscc failure"