diff --git a/clash-shake.cabal b/clash-shake.cabal
--- a/clash-shake.cabal
+++ b/clash-shake.cabal
@@ -3,11 +3,9 @@
 -- This file has been generated from package.yaml by hpack version 0.34.4.
 --
 -- see: https://github.com/sol/hpack
---
--- hash: 5f6e45bc2e072294d671a13e35cf938c8c9e4cfb32adee44eba24228b48bb9d6
 
 name:           clash-shake
-version:        0.1.0
+version:        0.1.1
 synopsis:       Shake rules for building Clash programs
 description:    Shake rules for building Clash programs and synthesizing FPGA
                 configuration. Contains build rules for Xilinx ISE and Xilinx Vivado
@@ -48,9 +46,6 @@
     , clash-lib >=1.4.2 && <1.5
     , clash-prelude >=1.4.2 && <1.5
     , directory
-    , ghc-typelits-extra
-    , ghc-typelits-knownnat
-    , ghc-typelits-natnormalise
     , shake
     , split
     , stache
diff --git a/src/Clash/Shake.hs b/src/Clash/Shake.hs
--- a/src/Clash/Shake.hs
+++ b/src/Clash/Shake.hs
@@ -7,6 +7,7 @@
     , SynthKit(..)
     , binImage
     , useConfig
+    , toolchain
     ) where
 
 import Development.Shake
@@ -17,6 +18,7 @@
 import qualified Clash.Main as Clash
 
 import Data.List.Split
+import Text.Printf
 
 import qualified Data.Text as T
 import qualified Data.HashMap.Strict as HM
@@ -46,6 +48,11 @@
 hdlExt Verilog = "v"
 hdlExt SystemVerilog = "sv"
 
+hdlClashFlag :: HDL -> String
+hdlClashFlag VHDL = "--vhdl"
+hdlClashFlag Verilog = "--verilog"
+hdlClashFlag SystemVerilog = "--systemverilog"
+
 data ClashKit = ClashKit
     { clash :: [String] -> Action ()
     , manifestSrcs :: Action [FilePath]
@@ -83,34 +90,30 @@
                             [ map toLower clashTopName <> "_types" | hdl == VHDL ]
             return [ synOut </> c <.> hdlExt hdl | c <- clashSrcs ]
 
-    getSrcs <- do
-        outDir </> "ghc-deps.make" %> \out -> do
-            alwaysRerun
-            -- By writing to a temp file and using `copyFileChanged`,
-            -- we avoid spurious reruns
-            -- (https://stackoverflow.com/a/64277431/477476)
-            withTempFileWithin outDir $ \tmp -> do
-                clash ["-M", "-dep-suffix", "", "-dep-makefile", tmp, src]
-                liftIO $ removeFiles outDir [takeBaseName tmp <.> "bak"]
-                copyFileChanged tmp out
-
-        return $ do
-            let depFile = outDir </> "ghc-deps.make"
-            need [depFile]
-            deps <- parseMakefile <$> liftIO (readFile depFile)
-            let isHsSource fn
-                  | ext `elem` [".hi"] = False
-                  | ext `elem` [".hs", ".lhs"] = True
-                  | otherwise = error $ "Unrecognized source file: " <> fn
-                  where
-                    ext = takeExtension fn
-                hsDeps = [fn | (_, fns) <- deps, fn <- fns, isHsSource fn]
-            return hsDeps
+    outDir </> "ghc-deps.make" %> \out -> do
+        alwaysRerun
+        -- By writing to a temp file and using `copyFileChanged`,
+        -- we avoid spurious reruns
+        -- (https://stackoverflow.com/a/64277431/477476)
+        withTempFileWithin outDir $ \tmp -> do
+            clash ["-M", "-dep-suffix", "", "-dep-makefile", tmp, src]
+            liftIO $ removeFiles outDir [takeBaseName tmp <.> "bak"]
+            copyFileChanged tmp out
 
     manifestFile %> \_out -> do
-        need =<< getSrcs
+        let depFile = outDir </> "ghc-deps.make"
+        need [depFile]
+        deps <- parseMakefile <$> liftIO (readFile depFile)
+        let isHsSource fn
+              | ext `elem` [".hi"] = False
+              | ext `elem` [".hs", ".lhs"] = True
+              | otherwise = error $ "Unrecognized source file: " <> fn
+              where
+                ext = takeExtension fn
+            hsDeps = [fn | (_, fns) <- deps, fn <- fns, isHsSource fn]
+        need hsDeps
         extraGenerated
-        clash [case hdl of { VHDL -> "--vhdl"; Verilog -> "--verilog"; SystemVerilog -> "--systemverilog" }, src]
+        clash [hdlClashFlag hdl, src]
 
     return ClashKit{..}
 
@@ -150,3 +153,13 @@
 
 isModuleName :: String -> Bool
 isModuleName = all (isUpper . head) . splitOn "."
+
+toolchain :: String -> FilePath -> [String] -> Action [String]
+toolchain name tool args = do
+    wrap <- getConfig name
+    root <- getConfig $ name <> "_ROOT"
+    let exe = case (wrap, root) of
+            (Just wrap, _) -> [wrap, tool]
+            (Nothing, Just root) -> [root </> tool]
+            (Nothing, Nothing) -> error $ printf "%s or %s must be set in build.mk" (name <> "_ROOT") name
+    return $ exe ++ args
diff --git a/src/Clash/Shake/Xilinx.hs b/src/Clash/Shake/Xilinx.hs
--- a/src/Clash/Shake/Xilinx.hs
+++ b/src/Clash/Shake/Xilinx.hs
@@ -49,14 +49,7 @@
     let projectName = topName
         rootDir = joinPath . map (const "..") . splitPath $ outDir
 
-    let ise tool args = do
-            root <- getConfig "ISE_ROOT"
-            wrap <- getConfig "ISE"
-            let exe = case (wrap, root) of
-                    (Just wrap, _) -> [wrap, tool]
-                    (Nothing, Just root) -> [root </> "ISE/bin/lin64" </> tool]
-                    (Nothing, Nothing) -> error "ISE_ROOT or ISE must be set in build.mk"
-            cmd_ (Cwd outDir) exe args
+    let ise tool args = cmd_ (Cwd outDir) =<< toolchain "ISE" tool args
 
     let getFiles dir pats = getDirectoryFiles srcDir [ dir </> pat | pat <- pats ]
         hdlSrcs = getFiles "src-hdl" ["*.vhdl", "*.v", "*.ucf" ]
@@ -114,14 +107,7 @@
         xpr = projectDir </> projectName <.> "xpr"
         rootDir = joinPath . map (const "..") . splitPath $ outDir
 
-    let vivado tool args = do
-            root <- getConfig "VIVADO_ROOT"
-            wrap <- getConfig "VIVADO"
-            let exe = case (wrap, root) of
-                    (Just wrap, _) -> [wrap, tool]
-                    (Nothing, Just root) -> [root </> "bin" </> tool]
-                    (Nothing, Nothing) -> error "VIVADO_ROOT or VIVADO must be set in build.mk"
-            cmd_ (Cwd outDir) exe args
+    let vivado tool args = cmd_ (Cwd outDir) =<< toolchain "VIVADO" tool args
         vivadoBatch tcl = do
             need [outDir </> tcl]
             vivado "vivado"