diff --git a/System/Process.hs b/System/Process.hs
--- a/System/Process.hs
+++ b/System/Process.hs
@@ -454,26 +454,31 @@
                     std_out = CreatePipe
                   }
     (ex, output) <- withCreateProcess_ "readCreateProcess" cp_opts $
-      \(Just inh) (Just outh) _ ph -> do
+      \mb_inh mb_outh _ ph ->
+        case (mb_inh, mb_outh) of
+          (Just inh, Just outh) -> do
 
-        -- fork off a thread to start consuming the output
-        output  <- hGetContents outh
-        withForkWait (C.evaluate $ rnf output) $ \waitOut -> do
+            -- fork off a thread to start consuming the output
+            output  <- hGetContents outh
+            withForkWait (C.evaluate $ rnf output) $ \waitOut -> do
 
-          -- now write any input
-          unless (null input) $
-            ignoreSigPipe $ hPutStr inh input
-          -- hClose performs implicit hFlush, and thus may trigger a SIGPIPE
-          ignoreSigPipe $ hClose inh
+              -- now write any input
+              unless (null input) $
+                ignoreSigPipe $ hPutStr inh input
+              -- hClose performs implicit hFlush, and thus may trigger a SIGPIPE
+              ignoreSigPipe $ hClose inh
 
-          -- wait on the output
-          waitOut
-          hClose outh
+              -- wait on the output
+              waitOut
+              hClose outh
 
-        -- wait on the process
-        ex <- waitForProcess ph
-        return (ex, output)
+            -- wait on the process
+            ex <- waitForProcess ph
+            return (ex, output)
 
+          (Nothing,_) -> error "readCreateProcess: Failed to get a stdin handle."
+          (_,Nothing) -> error "readCreateProcess: Failed to get a stdout handle."
+
     case ex of
      ExitSuccess   -> return output
      ExitFailure r -> processFailedException "readCreateProcess" cmd args r
@@ -486,7 +491,7 @@
              CreateProcess { cmdspec = RawCommand _ args' } -> args'
 
 
--- | @readProcessWithExitCode@ is like @readProcess@ but with two differences:
+-- | @readProcessWithExitCode@ is like 'readProcess' but with two differences:
 --
 --  * it returns the 'ExitCode' of the process, and does not throw any
 --    exception if the code is not 'ExitSuccess'.
@@ -523,32 +528,37 @@
                     std_err = CreatePipe
                   }
     withCreateProcess_ "readCreateProcessWithExitCode" cp_opts $
-      \(Just inh) (Just outh) (Just errh) ph -> do
+      \mb_inh mb_outh mb_errh ph ->
+        case (mb_inh, mb_outh, mb_errh) of
+          (Just inh, Just outh, Just errh) -> do
 
-        out <- hGetContents outh
-        err <- hGetContents errh
+            out <- hGetContents outh
+            err <- hGetContents errh
 
-        -- fork off threads to start consuming stdout & stderr
-        withForkWait  (C.evaluate $ rnf out) $ \waitOut ->
-         withForkWait (C.evaluate $ rnf err) $ \waitErr -> do
+            -- fork off threads to start consuming stdout & stderr
+            withForkWait  (C.evaluate $ rnf out) $ \waitOut ->
+             withForkWait (C.evaluate $ rnf err) $ \waitErr -> do
 
-          -- now write any input
-          unless (null input) $
-            ignoreSigPipe $ hPutStr inh input
-          -- hClose performs implicit hFlush, and thus may trigger a SIGPIPE
-          ignoreSigPipe $ hClose inh
+              -- now write any input
+              unless (null input) $
+                ignoreSigPipe $ hPutStr inh input
+              -- hClose performs implicit hFlush, and thus may trigger a SIGPIPE
+              ignoreSigPipe $ hClose inh
 
-          -- wait on the output
-          waitOut
-          waitErr
+              -- wait on the output
+              waitOut
+              waitErr
 
-          hClose outh
-          hClose errh
+              hClose outh
+              hClose errh
 
-        -- wait on the process
-        ex <- waitForProcess ph
+            -- wait on the process
+            ex <- waitForProcess ph
+            return (ex, out, err)
 
-        return (ex, out, err)
+          (Nothing,_,_) -> error "readCreateProcessWithExitCode: Failed to get a stdin handle."
+          (_,Nothing,_) -> error "readCreateProcessWithExitCode: Failed to get a stdout handle."
+          (_,_,Nothing) -> error "readCreateProcessWithExitCode: Failed to get a stderr handle."
 
 -- | Fork a thread while doing something else, but kill it if there's an
 -- exception.
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,10 @@
 # Changelog for [`process` package](http://hackage.haskell.org/package/process)
 
+## 1.6.5.1 *June 2019*
+
+* Version bound bumps
+* Slightly nicer error messages for internal errors
+
 ## 1.6.5.0 *December 2018*
 
 * Bug fix: On Windows ignore ERROR_ACCESS_DENIED for TerminateProcess() if the process did terminate
diff --git a/process.cabal b/process.cabal
--- a/process.cabal
+++ b/process.cabal
@@ -1,5 +1,5 @@
 name:          process
-version:       1.6.5.0
+version:       1.6.5.1
 -- NOTE: Don't forget to update ./changelog.md
 license:       BSD3
 license-file:  LICENSE
@@ -16,7 +16,7 @@
     which uses this package internally. It features better binary
     support, easier concurrency, and a more composable API. You can
     read more about it at
-    <https://haskell-lang.org/library/typed-process>.
+    <https://github.com/fpco/typed-process/#readme>.
 
 extra-source-files:
     aclocal.m4
@@ -60,7 +60,7 @@
         cpp-options: -DWINDOWS
     else
         other-modules: System.Process.Posix
-        build-depends: unix >= 2.5 && < 2.9
+        build-depends: unix >= 2.5 && < 2.8
 
     c-sources:
         cbits/runProcess.c
@@ -73,7 +73,7 @@
 
     ghc-options: -Wall
 
-    build-depends: base      >= 4.8.2 && < 4.13,
+    build-depends: base      >= 4.8.2 && < 4.14,
                    directory >= 1.1 && < 1.4,
                    filepath  >= 1.2 && < 1.5,
                    deepseq   >= 1.1 && < 1.5