diff --git a/Main.hs b/Main.hs
--- a/Main.hs
+++ b/Main.hs
@@ -156,7 +156,7 @@
       return ""
 
 processExitCode :: ExitCode -> IO ()
-processExitCode (ExitSuccess) = return ()
+processExitCode ExitSuccess = return ()
 processExitCode (ExitFailure n) = error $ "Error " ++ show n ++ " building dib.hs."
 
 rebuild :: Bool -> IO ()
diff --git a/dib.cabal b/dib.cabal
--- a/dib.cabal
+++ b/dib.cabal
@@ -1,5 +1,5 @@
 name:           dib
-version:        0.7.0
+version:        0.7.1
 cabal-version:  >= 1.6
 category:		Development
 build-type:     Simple
@@ -17,17 +17,17 @@
 source-repository this
   type: git
   location: https://github.com/blajzer/dib.git
-  tag: 0.7.0
+  tag: 0.7.1
 
 library
-  build-depends:   base >= 4.4 && < 4.10, text, containers, mtl, directory, time, process, filepath, cereal, bytestring, digest
+  build-depends:   base >= 4.4 && < 4.11, text, containers, mtl, directory, time, process, filepath, cereal, bytestring, digest
   ghc-options:     -Wall
   hs-source-dirs:  src
   exposed-modules: Dib, Dib.Gatherers, Dib.Stage, Dib.Target, Dib.Types, Dib.Scanners.CDepScanner, Dib.Builders.C, Dib.Builders.Copy, Dib.Builders.Simple, Dib.Util
   extensions:      OverloadedStrings
 
 executable dib
-  build-depends:   base >= 4.4 && < 4.10, containers, mtl, time, directory, filepath
+  build-depends:   base >= 4.4 && < 4.11, containers, mtl, time, directory, filepath
   ghc-options:     -Wall
   hs-source-dirs:  .
   main-is:         Main.hs
diff --git a/src/Dib.hs b/src/Dib.hs
--- a/src/Dib.hs
+++ b/src/Dib.hs
@@ -135,17 +135,18 @@
   numProcs <- GHC.getNumProcessors
 
   -- Validate that we have at least one target
-  if targets == [] then putStrLn $ "ERROR: Invalid configuration, no targets defined." else do
+  if null targets then putStrLn "ERROR: Invalid configuration, no targets defined." else do
 
   let allTargets = gatherAllTargets targets
-  let buildArgs = parseArgs args allTargets numProcs
-  let selectedTarget = buildTarget buildArgs
-  let theTarget = L.find (\(Target name _ _ _ _) -> name == selectedTarget) allTargets
 
   -- Validate targets
   let targetErrors = validateTargets allTargets
   if isJust targetErrors then putStrLn $ "ERROR: Invalid targets:\n" ++ fromJust targetErrors else do
 
+  let buildArgs = parseArgs args allTargets numProcs
+  let selectedTarget = buildTarget buildArgs
+  let theTarget = L.find (\(Target name _ _ _ _) -> name == selectedTarget) allTargets
+
   -- Validate that we're trying to build something that exists
   if isNothing theTarget then putStrLn $ "ERROR: Invalid target specified: \"" ++ T.unpack selectedTarget ++ "\"" else do
 
@@ -183,7 +184,7 @@
 validateTargets :: [Target] -> Maybe String
 validateTargets ts =
   let targetErrors = L.foldl' (\acc t -> acc ++ validate t) "" ts
-      validate (Target name _ _ stages gatherers) = if length stages > 0 && length gatherers == 0 then (T.unpack name) ++ ": target requires at least one gatherer since it specifies at least one stage.\n" else ""
+      validate (Target name _ _ stages gatherers) = if not (null stages) && null gatherers then T.unpack name ++ ": target requires at least one gatherer since it specifies at least one stage.\n" else ""
   in if targetErrors == "" then Nothing else Just targetErrors
 
 extractVarsFromArgs :: [String] -> ArgDict
@@ -232,10 +233,7 @@
 makeArgDictLookupFuncChecked arg defVal validValues dict =
     let partialResult = makeArgDictLookupFunc arg defVal dict
         result = L.find (== partialResult) validValues
-    in if isJust result then
-        Right $ fromJust result
-      else
-        Left $ "ERROR: invalid value \"" ++ partialResult ++ "\" for argument \"" ++ arg ++ "\". Expected one of: [" ++ L.intercalate  ", " validValues ++ "]"
+    in maybe (Left $ "ERROR: invalid value \"" ++ partialResult ++ "\" for argument \"" ++ arg ++ "\". Expected one of: [" ++ L.intercalate  ", " validValues ++ "]") Right result
 
 printSeparator :: IO ()
 printSeparator = putStrLn "============================================================"
diff --git a/src/Dib/Builders/C.hs b/src/Dib/Builders/C.hs
--- a/src/Dib/Builders/C.hs
+++ b/src/Dib/Builders/C.hs
@@ -25,7 +25,6 @@
 import Data.Word
 import System.Process (system)
 import System.Directory as D
-import System.Exit
 import System.FilePath as F
 
 import qualified Data.Digest.CRC32 as Hash
@@ -246,7 +245,7 @@
   in Target (targetName info) (cTargetHash info) [] [cppStage, if staticLibrary info then archiveStage else linkStage] [buildDirGatherer, makeFileTreeGatherer (srcDir info) (matchExtensionsExcluded [".cpp", ".c"] [excludeFiles $ exclusions info])]
 
 changeExt :: T.Text -> BuildLocation -> SrcTransform -> SrcTransform
-changeExt newExt b (OneToOne l _) = OneToOne l $ remapObjFile b $ (T.dropWhileEnd (/='.') l)  <> newExt
+changeExt newExt b (OneToOne l _) = OneToOne l $ remapObjFile b $ T.dropWhileEnd (/='.') l <> newExt
 changeExt _ _ _ = undefined
 
 combineTransforms :: T.Text -> [SrcTransform] -> [SrcTransform]
diff --git a/src/Dib/Builders/Simple.hs b/src/Dib/Builders/Simple.hs
--- a/src/Dib/Builders/Simple.hs
+++ b/src/Dib/Builders/Simple.hs
@@ -15,7 +15,6 @@
 import qualified Data.Text as T
 import qualified System.Directory as D
 import System.Process (system)
-import System.Exit
 import System.FilePath as P
 
 buildFunc :: (String -> String -> String) -> SrcTransform -> IO StageResult
diff --git a/src/Dib/Types.hs b/src/Dib/Types.hs
--- a/src/Dib/Types.hs
+++ b/src/Dib/Types.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE GeneralizedNewtypeDeriving, ExistentialQuantification, OverloadedStrings #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving, ExistentialQuantification #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 {-# OPTIONS_HADDOCK hide, prune #-}
 
@@ -117,7 +117,7 @@
 type FilterFunc = (T.Text -> Bool)
 
 -- | 'Gatherer' that will return exactly one file.
-data SingleFileGatherer = SingleFileGatherer T.Text
+newtype SingleFileGatherer = SingleFileGatherer T.Text
 
 -- | 'Gatherer' that will return all files in a given directory (but not its
 -- subdirectories) that pass the filter.
@@ -129,7 +129,7 @@
 
 -- | 'Gatherer' that will run a command and return an empty list.
 -- Useful for making clean 'Target's. Use sparingly.
-data CommandGatherer = CommandGatherer (IO ())
+newtype CommandGatherer = CommandGatherer (IO ())
 
 -- Horrible.
 instance Serialize.Serialize T.Text where