diff --git a/CHANGES.txt b/CHANGES.txt
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,5 +1,10 @@
 Changelog for Shake (* = breaking change)
 
+0.19.1, released 2020-06-06
+    #757, make sure shared cache writes are atomic
+    Remove a small space leak if using the Database module
+    #755, add instance IsCmdArgument (NonEmpty String)
+    #754, tighten bounds to exclude GHC 7.10
 0.19, released 2020-05-23
     #738, improve the help text
     #679, allow Ninja to depend on a directory
diff --git a/shake.cabal b/shake.cabal
--- a/shake.cabal
+++ b/shake.cabal
@@ -1,7 +1,7 @@
 cabal-version:      >= 1.18
 build-type:         Simple
 name:               shake
-version:            0.19
+version:            0.19.1
 license:            BSD3
 license-file:       LICENSE
 category:           Development, Shake
@@ -85,7 +85,7 @@
     default-language: Haskell2010
     hs-source-dirs:   src
     build-depends:
-        base >= 4.8,
+        base >= 4.9,
         binary,
         bytestring,
         deepseq >= 1.1,
diff --git a/src/Development/Ninja/All.hs b/src/Development/Ninja/All.hs
--- a/src/Development/Ninja/All.hs
+++ b/src/Development/Ninja/All.hs
@@ -93,7 +93,7 @@
 resolvePhony mp = f $ Left 100
     where
         f (Left 0) x = f (Right []) x
-        f (Right xs) x | x `elem` xs = error $ "Recursive phony involving " ++ BS.unpack x
+        f (Right xs) x | x `elem` xs = error $ "Ninja recursive phony involving " ++ BS.unpack x
         f a x = case Map.lookup x mp of
             Nothing -> [x]
             Just xs -> concatMap (f $ either (Left . subtract 1) (Right . (x:)) a) xs
diff --git a/src/Development/Ninja/Lexer.hs b/src/Development/Ninja/Lexer.hs
--- a/src/Development/Ninja/Lexer.hs
+++ b/src/Development/Ninja/Lexer.hs
@@ -164,7 +164,7 @@
     , ('=',x) <- list0 $ jumpCont $ dropSpace x
     , (exp,x) <- lexxExpr False False $ jumpCont $ dropSpace x
     = ctor var exp : lexerLoop x
-lexxBind _ x = error $ show ("parse failed when parsing binding", take0 100 x)
+lexxBind _ x = error $ "Ninja parse failed when parsing binding, " ++ show (take0 100 x)
 
 lexxFile :: (Expr -> Lexeme) -> Str0 -> [Lexeme]
 lexxFile ctor x
@@ -182,11 +182,11 @@
     (a,c_x) | c <- head0 c_x, x <- tail0 c_x -> case c of
         ' ' -> add a $ lexxExprs stopColon $ dropSpace x
         ':' | stopColon -> new a x
-        _ | stopColon -> error "expected a colon"
+        _ | stopColon -> error "Ninja parsing, expected a colon"
         '\r' -> new a $ dropN x
         '\n' -> new a x
         '\0' -> new a c_x
-        _ -> error "unexpected expression in Ninja"
+        _ -> error "Ninja parsing, unexpected expression"
     where
         new a x = add a ([], x)
         add (Exprs []) x = x
@@ -218,7 +218,7 @@
             '\r' -> f $ dropSpace $ dropN x
             '{' | (name,x) <- span0 isVarDot x, not $ BS.null name, ('}',x) <- list0 x -> Var name $: f x
             _ | (name,x) <- span0 isVar c_x, not $ BS.null name -> Var name $: f x
-            _ -> error "Unexpect $ followed by unexpected stuff"
+            _ -> error "Ninja parsing, unexpect $ followed by unexpected stuff"
 
 jumpCont :: Str0 -> Str0
 jumpCont o
diff --git a/src/Development/Ninja/Parse.hs b/src/Development/Ninja/Parse.hs
--- a/src/Development/Ninja/Parse.hs
+++ b/src/Development/Ninja/Parse.hs
@@ -58,7 +58,7 @@
         addBind env a b
         pure ninja
     LexBind a _ ->
-        error $ "Unexpected binding defining " ++ BS.unpack a
+        error $ "Ninja parsing, unexpected binding defining " ++ BS.unpack a
 
 
 splitDeps :: [Str] -> ([Str], [Str], [Str])
@@ -76,4 +76,4 @@
         x <- askExpr env x
         case BS.readInt x of
             Just (i, n) | BS.null n -> pure i
-            _ -> error $ "Could not parse depth field in pool, got: " ++ BS.unpack x
+            _ -> error $ "Ninja parsing, could not parse depth field in pool, got: " ++ BS.unpack x
diff --git a/src/Development/Shake/Command.hs b/src/Development/Shake/Command.hs
--- a/src/Development/Shake/Command.hs
+++ b/src/Development/Shake/Command.hs
@@ -26,7 +26,9 @@
 import Control.Exception.Extra
 import Data.Char
 import Data.Either.Extra
+import Data.Foldable (toList)
 import Data.List.Extra
+import Data.List.NonEmpty (NonEmpty)
 import Data.Maybe
 import Data.Data
 import Data.Semigroup
@@ -38,7 +40,7 @@
 import System.Process
 import System.Info.Extra
 import System.Time.Extra
-import System.IO.Unsafe(unsafeInterleaveIO)
+import System.IO.Unsafe (unsafeInterleaveIO)
 import qualified Data.ByteString.Char8 as BS
 import qualified Data.ByteString.Lazy.Char8 as LBS
 import qualified Data.ByteString.UTF8 as UTF8
@@ -740,6 +742,7 @@
 instance IsCmdArgument () where toCmdArgument = mempty
 instance IsCmdArgument String where toCmdArgument = CmdArgument . map Right . words
 instance IsCmdArgument [String] where toCmdArgument = CmdArgument . map Right
+instance IsCmdArgument (NonEmpty String) where toCmdArgument = toCmdArgument . toList
 instance IsCmdArgument CmdOption where toCmdArgument = CmdArgument . pure . Left
 instance IsCmdArgument [CmdOption] where toCmdArgument = CmdArgument . map Left
 instance IsCmdArgument CmdArgument where toCmdArgument = id
@@ -754,4 +757,4 @@
 showCommandForUser2 cmd args = unwords $ map (\x -> if safe x then x else showCommandForUser x []) $ cmd : args
     where
         safe xs = xs /= "" && not (any bad xs)
-        bad x = isSpace x || (x == '\\' && not isWindows) || x `elem` "\"\'"
+        bad x = isSpace x || (x == '\\' && not isWindows) || x `elem` ("\"\'" :: String)
diff --git a/src/Development/Shake/Internal/Core/Rules.hs b/src/Development/Shake/Internal/Core/Rules.hs
--- a/src/Development/Shake/Internal/Core/Rules.hs
+++ b/src/Development/Shake/Internal/Core/Rules.hs
@@ -220,12 +220,17 @@
 --   See 'addBuiltinRule' and 'Development.Shake.Rule.apply'.
 type family RuleResult key -- = value
 
--- | Define a builtin rule, passing the functions to run in the right circumstances.
+-- | Before looking at this function, you should read the warnings at the top of this module.
+--   This function is not often necessary in build systems.
+--
+--   Define a builtin rule, passing the functions to run in the right circumstances.
 --   The @key@ and @value@ types will be what is used by 'Development.Shake.Rule.apply'.
 --   As a start, you can use 'noLint' and 'noIdentity' as the first two functions,
 --   but are required to supply a suitable 'BuiltinRun'.
 --
 --   Raises an error if any other rule exists at this type.
+--
+--   For a worked example of writing a rule see <https://tech-blog.capital-match.com/posts/5-upgrading-shake.html>.
 addBuiltinRule
     :: (RuleResult key ~ value, ShakeValue key, Typeable value, NFData value, Show value, Partial)
     => BuiltinLint key value -> BuiltinIdentity key value -> BuiltinRun key value -> Rules ()
diff --git a/src/Development/Shake/Internal/Core/Run.hs b/src/Development/Shake/Internal/Core/Run.hs
--- a/src/Development/Shake/Internal/Core/Run.hs
+++ b/src/Development/Shake/Internal/Core/Run.hs
@@ -331,7 +331,7 @@
 incrementStep db = runLocked db $ do
     stepId <- mkId db stepKey
     v <- liftIO $ getKeyValueFromId db stepId
-    step<- pure $ case v of
+    step <- liftIO $ evaluate $ case v of
         Just (_, Loaded r) -> incStep $ fromStepResult r
         _ -> Step 1
     let stepRes = toStepResult step
diff --git a/src/Development/Shake/Internal/Core/Storage.hs b/src/Development/Shake/Internal/Core/Storage.hs
--- a/src/Development/Shake/Internal/Core/Storage.hs
+++ b/src/Development/Shake/Internal/Core/Storage.hs
@@ -71,7 +71,7 @@
     ,"All rules will be rebuilt"]
     where
         limit x = let (a,b) = splitAt 200 x in a ++ (if null b then "" else "...")
-        disp = map (\x -> if isPrint x && isAscii x then x else '?') . takeWhile (`notElem` "\r\n")
+        disp = map (\x -> if isPrint x && isAscii x then x else '?') . takeWhile (`notElem` ("\r\n" :: String))
 
 
 messageMissingTypes :: FilePath -> [String] -> [String]
diff --git a/src/Development/Shake/Internal/Core/Types.hs b/src/Development/Shake/Internal/Core/Types.hs
--- a/src/Development/Shake/Internal/Core/Types.hs
+++ b/src/Development/Shake/Internal/Core/Types.hs
@@ -207,10 +207,10 @@
 type OneShot a = a
 
 data Status
-    = Ready (Result (Value, OneShot BS_Store)) -- ^ I have a value
-    | Failed SomeException (OneShot (Maybe (Result BS_Store))) -- ^ I have been run and raised an error
-    | Loaded (Result BS_Store) -- ^ Loaded from the database
-    | Running (NoShow (Either SomeException (Result (Value, BS_Store)) -> Locked ())) (Maybe (Result BS_Store)) -- ^ Currently in the process of being checked or built
+    = Ready !(Result (Value, OneShot BS_Store)) -- ^ I have a value
+    | Failed !SomeException !(OneShot (Maybe (Result BS_Store))) -- ^ I have been run and raised an error
+    | Loaded !(Result BS_Store) -- ^ Loaded from the database
+    | Running !(NoShow (Either SomeException (Result (Value, BS_Store)) -> Locked ())) (Maybe (Result BS_Store)) -- ^ Currently in the process of being checked or built
     | Missing -- ^ I am only here because I got into the Intern table
       deriving Show
 
@@ -227,12 +227,12 @@
 
 
 data Result a = Result
-    {result :: a -- ^ the result associated with the Key
+    {result :: !a -- ^ the result associated with the Key
     ,built :: {-# UNPACK #-} !Step -- ^ when it was actually run
     ,changed :: {-# UNPACK #-} !Step -- ^ the step for deciding if it's valid
-    ,depends :: [Depends] -- ^ dependencies (don't run them early)
+    ,depends :: ![Depends] -- ^ dependencies (don't run them early)
     ,execution :: {-# UNPACK #-} !Float -- ^ how long it took when it was last run (seconds)
-    ,traces :: [Trace] -- ^ a trace of the expensive operations (start/end in seconds since beginning of run)
+    ,traces :: ![Trace] -- ^ a trace of the expensive operations (start/end in seconds since beginning of run)
     } deriving (Show,Functor)
 
 instance NFData a => NFData (Result a) where
diff --git a/src/Development/Shake/Internal/Demo.hs b/src/Development/Shake/Internal/Demo.hs
--- a/src/Development/Shake/Internal/Demo.hs
+++ b/src/Development/Shake/Internal/Demo.hs
@@ -27,7 +27,7 @@
     hasManual <- hasManualData
     ghc <- isJust <$> findExecutable "ghc"
     (gcc, gccPath) <- findGcc
-    shakeLib <- wrap $ fmap (not . null . words . fromStdout) (cmd "ghc-pkg list --simple-output shake")
+    shakeLib <- wrap $ fmap (not . null . words . fromStdout) (cmd ("ghc-pkg list --simple-output shake" :: String))
     ninja <- findExecutable "ninja"
     putStrLn "done\n"
 
diff --git a/src/Development/Shake/Internal/History/Shared.hs b/src/Development/Shake/Internal/History/Shared.hs
--- a/src/Development/Shake/Internal/History/Shared.hs
+++ b/src/Development/Shake/Internal/History/Shared.hs
@@ -19,7 +19,7 @@
 import Control.Monad.Extra
 import System.Directory.Extra
 import System.FilePath
-import System.IO
+import System.IO.Extra
 import Numeric
 import Development.Shake.Internal.FileInfo
 import General.Wait
@@ -136,8 +136,11 @@
             copyFileLink (useSymlink shared) file (dir </> show hash)
     -- Write key after files to make sure cache is always useable
     let v = runBuilder $ putEntry (keyOp shared) entry
-    createDirectoryRecursive $ dir </> "_key"
-    BS.writeFile (dir </> "_key" </> hexed v) v
+    let dirName = dir </> "_key"
+    createDirectoryRecursive dirName
+    -- #757, make sure we write this file atomically
+    (tempFile, cleanUp) <- newTempFileWithin dir
+    (BS.writeFile tempFile v >> renameFile tempFile (dirName </> hexed v)) `onException` cleanUp
 
 
 addShared :: Shared -> Key -> Ver -> Ver -> [[(Key, BS_Identity)]] -> BS_Store -> [FilePath] -> IO ()
diff --git a/src/Development/Shake/Internal/Options.hs b/src/Development/Shake/Internal/Options.hs
--- a/src/Development/Shake/Internal/Options.hs
+++ b/src/Development/Shake/Internal/Options.hs
@@ -18,6 +18,7 @@
 import System.Time.Extra
 import qualified Data.HashMap.Strict as Map
 import Development.Shake.Internal.FilePattern
+import Development.Shake.Internal.Errors
 import qualified Data.ByteString.Char8 as BS
 import qualified Data.ByteString.UTF8 as UTF8
 import Development.Shake.Internal.CmdOption
@@ -285,7 +286,7 @@
             | Just x <- cast x = show (x :: Hidden (Map.HashMap TypeRep Dynamic))
             | Just x <- cast x = show (x :: Hidden (String -> String -> Bool -> IO ()))
             | Just x <- cast x = show (x :: [CmdOption])
-            | otherwise = error $ "Error while showing ShakeOptions, missing alternative for " ++ show (typeOf x)
+            | otherwise = throwImpure $ errorInternal $ "Error while showing ShakeOptions, missing alternative for " ++ show (typeOf x)
 
 instance Show ShakeOptions where
     show x = "ShakeOptions {" ++ intercalate ", " (map (\(a,b) -> a ++ " = " ++ b) $ shakeOptionsFields x) ++ "}"
diff --git a/src/Development/Shake/Internal/Profile.hs b/src/Development/Shake/Internal/Profile.hs
--- a/src/Development/Shake/Internal/Profile.hs
+++ b/src/Development/Shake/Internal/Profile.hs
@@ -41,7 +41,7 @@
         (noDeps, hasDeps) = partition (null . snd) $ Map.toList status
 
         f [] mp | null bad = []
-                | otherwise = error $ unlines $
+                | otherwise = throwImpure $ errorInternal $ unlines $
                     "Internal invariant broken, database seems to be cyclic" :
                     map ("    " ++) bad ++
                     ["... plus " ++ show (length badOverflow) ++ " more ..." | not $ null badOverflow]
diff --git a/src/Development/Shake/Internal/Value.hs b/src/Development/Shake/Internal/Value.hs
--- a/src/Development/Shake/Internal/Value.hs
+++ b/src/Development/Shake/Internal/Value.hs
@@ -12,7 +12,6 @@
 import Development.Shake.Internal.Errors
 import Data.Typeable
 
-import Data.Bits
 import Unsafe.Coerce
 
 
@@ -103,7 +102,8 @@
     rnf Value{..} = valueRnf valueValue
 
 instance Hashable Key where
-    hashWithSalt salt Key{..} = hashWithSalt salt keyType `xor` keyHash salt keyValue
+    hash Key{..} = keyHash (hash keyType) keyValue
+    hashWithSalt salt Key{..} = keyHash (hashWithSalt salt keyType) keyValue
 
 instance Eq Key where
     Key{keyType=at,keyValue=a,keyEq=eq} == Key{keyType=bt,keyValue=b}
diff --git a/src/General/Extra.hs b/src/General/Extra.hs
--- a/src/General/Extra.hs
+++ b/src/General/Extra.hs
@@ -275,7 +275,7 @@
 
 
 -- | Invert 'prettyCallStack', which GHC pre-applies in certain cases
-parseCallStack = reverse . map trimStart . drop 1 . lines
+parseCallStack = reverse . map trimStart . drop1 . lines
 
 callStackFull = parseCallStack $ prettyCallStack $ popCallStack callStack
 
diff --git a/src/General/Ids.hs b/src/General/Ids.hs
--- a/src/General/Ids.hs
+++ b/src/General/Ids.hs
@@ -99,7 +99,7 @@
     let go !i | i >= used = pure ()
               | otherwise = do
                 v <- readArray values i
-                whenJust v $ \v -> writeArray values i $ Just $ f v
+                whenJust v $ \v -> writeArray values i $! Just $! f v
                 go $ i+1
     go 0
 
diff --git a/src/Test/Pool.hs b/src/Test/Pool.hs
--- a/src/Test/Pool.hs
+++ b/src/Test/Pool.hs
@@ -100,6 +100,6 @@
         resetTimings
         withNumCapabilities 4 $ do
             (d, _) <- duration $ runPool False 4 $ \pool ->
-                replicateM_ 200000 $ addPool PoolStart pool $ return ()
+                replicateM_ 200000 $ addPool PoolStart pool $ pure ()
             print d
             print =<< getTimings