diff --git a/package.yaml b/package.yaml
--- a/package.yaml
+++ b/package.yaml
@@ -1,5 +1,5 @@
 name: stack
-version: '1.6.1'
+version: '1.6.1.1'
 synopsis: The Haskell Tool Stack
 description: ! 'Please see the README.md for usage information, and
   the wiki on Github for more details.  Also, note that
diff --git a/src/Control/Concurrent/Execute.hs b/src/Control/Concurrent/Execute.hs
--- a/src/Control/Concurrent/Execute.hs
+++ b/src/Control/Concurrent/Execute.hs
@@ -11,7 +11,7 @@
     , runActions
     ) where
 
-import           Control.Concurrent.STM
+import           Control.Concurrent.STM   (retry)
 import           Stack.Prelude
 import qualified Data.Set                 as Set
 import           Stack.Types.PackageIdentifier
diff --git a/src/Network/HTTP/Download/Verified.hs b/src/Network/HTTP/Download/Verified.hs
--- a/src/Network/HTTP/Download/Verified.hs
+++ b/src/Network/HTTP/Download/Verified.hs
@@ -49,7 +49,6 @@
 import              Stack.PrettyPrint
 import              System.Directory
 import qualified    System.FilePath as FP ((<.>))
-import              System.IO (hFileSize)
 
 -- | A request together with some checks to perform.
 data DownloadRequest = DownloadRequest
diff --git a/src/Stack/Build/Execute.hs b/src/Stack/Build/Execute.hs
--- a/src/Stack/Build/Execute.hs
+++ b/src/Stack/Build/Execute.hs
@@ -24,7 +24,7 @@
     ) where
 
 import           Control.Concurrent.Execute
-import           Control.Concurrent.STM
+import           Control.Concurrent.STM (check)
 import           Stack.Prelude
 import           Crypto.Hash
 import           Data.Attoparsec.Text hiding (try)
@@ -84,7 +84,7 @@
 import           System.Environment (getExecutablePath)
 import           System.Exit (ExitCode (ExitSuccess))
 import qualified System.FilePath as FP
-import           System.IO
+import           System.IO (hPutStr, openBinaryFile)
 import           System.PosixCompat.Files (createLink)
 import           System.Process.Log (showProcessArgDebug, withProcessTimeLog)
 import           System.Process.Read
diff --git a/src/Stack/Docker.hs b/src/Stack/Docker.hs
--- a/src/Stack/Docker.hs
+++ b/src/Stack/Docker.hs
@@ -58,7 +58,7 @@
 import           System.Environment (getEnv,getEnvironment,getProgName,getArgs,getExecutablePath)
 import           System.Exit (exitSuccess, exitWith, ExitCode(..))
 import qualified System.FilePath as FP
-import           System.IO (stderr,stdin,stdout,hIsTerminalDevice, hClose)
+import           System.IO (stderr,stdin,stdout)
 import           System.IO.Error (isDoesNotExistError)
 import           System.IO.Unsafe (unsafePerformIO)
 import qualified System.PosixCompat.User as User
diff --git a/src/Stack/Fetch.hs b/src/Stack/Fetch.hs
--- a/src/Stack/Fetch.hs
+++ b/src/Stack/Fetch.hs
@@ -33,7 +33,6 @@
 import qualified    Codec.Archive.Tar.Check as Tar
 import qualified    Codec.Archive.Tar.Entry as Tar
 import              Codec.Compression.GZip (decompress)
-import              Control.Concurrent.STM
 import              Stack.Prelude
 import              Crypto.Hash (SHA256 (..))
 import qualified    Data.ByteString as S
@@ -62,7 +61,7 @@
 import              Stack.Types.Runner
 import              Stack.Types.Version
 import qualified    System.FilePath as FP
-import              System.IO (hSeek, SeekMode (AbsoluteSeek))
+import              System.IO (SeekMode (AbsoluteSeek))
 import              System.PosixCompat (setFileMode)
 
 data FetchException
diff --git a/src/Stack/FileWatch.hs b/src/Stack/FileWatch.hs
--- a/src/Stack/FileWatch.hs
+++ b/src/Stack/FileWatch.hs
@@ -9,13 +9,12 @@
 
 import Blaze.ByteString.Builder (toLazyByteString, copyByteString)
 import Blaze.ByteString.Builder.Char.Utf8 (fromShow)
-import Control.Concurrent.STM
+import Control.Concurrent.STM (check)
 import Stack.Prelude
 import qualified Data.ByteString.Lazy as L
 import qualified Data.Map.Strict as Map
 import qualified Data.Set as Set
 import GHC.IO.Exception
-import GHC.IO.Handle (hIsTerminalDevice)
 import Path
 import System.Console.ANSI
 import System.FSNotify
diff --git a/src/Stack/Ghci/Script.hs b/src/Stack/Ghci/Script.hs
--- a/src/Stack/Ghci/Script.hs
+++ b/src/Stack/Ghci/Script.hs
@@ -21,7 +21,7 @@
 import           Data.Text.Encoding (encodeUtf8Builder)
 import           Path
 import           Stack.Prelude hiding (ByteString)
-import           System.IO (hSetBuffering, BufferMode (..), hSetBinaryMode)
+import           System.IO (BufferMode (..), hSetBinaryMode)
 
 import           Distribution.ModuleName hiding (toFilePath)
 
diff --git a/src/Stack/Setup.hs b/src/Stack/Setup.hs
--- a/src/Stack/Setup.hs
+++ b/src/Stack/Setup.hs
@@ -94,7 +94,7 @@
 import qualified    System.Directory as D
 import              System.Environment (getExecutablePath, lookupEnv)
 import              System.Exit (ExitCode (..), exitFailure)
-import              System.IO (hFlush, stdout)
+import              System.IO (stdout)
 import              System.IO.Error (isPermissionError)
 import              System.FilePath (searchPathSeparator)
 import qualified    System.FilePath as FP
diff --git a/src/Stack/Types/Runner.hs b/src/Stack/Types/Runner.hs
--- a/src/Stack/Types/Runner.hs
+++ b/src/Stack/Types/Runner.hs
@@ -46,7 +46,7 @@
 import           Stack.Types.PackageIdentifier (PackageIdentifierRevision)
 import           System.Console.ANSI
 import           System.FilePath
-import           System.IO
+import           System.IO                  (localeEncoding)
 import           System.Log.FastLogger
 import           System.Terminal
 
diff --git a/src/Stack/Upload.hs b/src/Stack/Upload.hs
--- a/src/Stack/Upload.hs
+++ b/src/Stack/Upload.hs
@@ -47,7 +47,7 @@
 import           System.Directory                      (createDirectoryIfMissing,
                                                         removeFile)
 import           System.FilePath                       ((</>), takeFileName)
-import           System.IO                             (hFlush, stdout, putStrLn, putStr, getLine, print) -- TODO remove putStrLn, use logInfo
+import           System.IO                             (stdout, putStrLn, putStr, getLine, print) -- TODO remove putStrLn, use logInfo
 import           System.IO.Echo                        (withoutInputEcho)
 
 -- | Username and password to log into Hackage.
diff --git a/src/System/Process/PagerEditor.hs b/src/System/Process/PagerEditor.hs
--- a/src/System/Process/PagerEditor.hs
+++ b/src/System/Process/PagerEditor.hs
@@ -28,7 +28,7 @@
 import System.FilePath ((</>))
 import System.Process (createProcess,shell,proc,waitForProcess,StdStream (CreatePipe)
                       ,CreateProcess(std_in, close_fds, delegate_ctlc))
-import System.IO (hClose,hPutStr,readFile,stdout)
+import System.IO (hPutStr,readFile,stdout)
 
 -- | Run pager, providing a function that writes to the pager's input.
 pageWriter :: (Handle -> IO ()) -> IO ()
diff --git a/src/System/Process/Read.hs b/src/System/Process/Read.hs
--- a/src/System/Process/Read.hs
+++ b/src/System/Process/Read.hs
@@ -57,7 +57,6 @@
 import           System.Environment (getEnvironment)
 import           System.Exit
 import qualified System.FilePath as FP
-import           System.IO (hClose)
 import           System.Process.Log
 
 -- | Override the environment received by a child process.
diff --git a/src/System/Process/Run.hs b/src/System/Process/Run.hs
--- a/src/System/Process/Run.hs
+++ b/src/System/Process/Run.hs
@@ -23,7 +23,7 @@
 import           Data.Conduit.Process hiding (callProcess)
 import qualified Data.Text as T
 import           System.Exit (exitWith, ExitCode (..))
-import           System.IO
+import           System.IO (hGetLine)
 import qualified System.Process
 import           System.Process.Log
 import           System.Process.Read
diff --git a/src/main/Main.hs b/src/main/Main.hs
--- a/src/main/Main.hs
+++ b/src/main/Main.hs
@@ -105,7 +105,7 @@
 import           System.Environment (getProgName, getArgs, withArgs)
 import           System.Exit
 import           System.FilePath (isValid, pathSeparator)
-import           System.IO (hIsTerminalDevice, stderr, stdin, stdout, hSetBuffering, BufferMode(..), hPutStrLn, hGetEncoding, hSetEncoding)
+import           System.IO (stderr, stdin, stdout, BufferMode(..), hPutStrLn, hGetEncoding, hSetEncoding)
 
 -- | Change the character encoding of the given Handle to transliterate
 -- on unsupported characters instead of throwing an exception
diff --git a/src/test/Stack/StoreSpec.hs b/src/test/Stack/StoreSpec.hs
--- a/src/test/Stack/StoreSpec.hs
+++ b/src/test/Stack/StoreSpec.hs
@@ -51,7 +51,7 @@
     (if (minBound :: a) `notElem` xs then [minBound] else []) ++
     (if (maxBound :: a) `notElem` xs && (maxBound :: a) /= minBound then maxBound : xs else xs)
 
-$(do let ns = [ ''Int64, ''Word64, ''Word, ''Word8
+$(do let ns = [ ''Int64, ''Word64, ''Word8
               ]
          f n = [d| instance Monad m => Serial m $(conT n) where
                       series = generate (\_ -> addMinAndMaxBounds [0, 1]) |]
diff --git a/stack.cabal b/stack.cabal
--- a/stack.cabal
+++ b/stack.cabal
@@ -2,10 +2,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: d149de7c99c88786c765e40f4d0f24a47010c288e64c6cb556d989a04a0df537
+-- hash: de62cea79534de3d9c9e0479c0650a4159c588e37a8ae05df6dab12a1a5f0c46
 
 name:           stack
-version:        1.6.1
+version:        1.6.1.1
 synopsis:       The Haskell Tool Stack
 description:    Please see the README.md for usage information, and the wiki on Github for more details.  Also, note that the API for the library is not currently stable, and may change significantly, even between minor releases. It is currently only intended for use by the executable.
 category:       Development
diff --git a/stack.yaml b/stack.yaml
--- a/stack.yaml
+++ b/stack.yaml
@@ -26,6 +26,7 @@
 - extra-1.6
 - hsc2hs-0.68.2
 - hpack-0.20.0
-- unliftio-0.2.0.0
+- unliftio-0.2.1.0
 - ansi-terminal-0.7.1.1
 - ansi-wl-pprint-0.6.8.1
+- smallcheck-1.1.3
