diff --git a/System/Win32/FileMapping.hsc b/System/Win32/FileMapping.hsc
--- a/System/Win32/FileMapping.hsc
+++ b/System/Win32/FileMapping.hsc
@@ -1,4 +1,8 @@
+#if __GLASGOW_HASKELL__ >= 709
+{-# LANGUAGE Safe #-}
+#else
 {-# LANGUAGE Trustworthy #-}
+#endif
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  System.Win32.FileMapping
@@ -22,8 +26,6 @@
 import System.Win32.Info
 
 import Control.Exception        ( mask_, bracket )
-import Data.ByteString          ( ByteString )
-import Data.ByteString.Internal ( fromForeignPtr )
 import Foreign                  ( Ptr, nullPtr, plusPtr, maybeWith, FunPtr
                                 , ForeignPtr, newForeignPtr )
 import Foreign.C.Types (CUIntPtr(..))
@@ -52,12 +54,6 @@
                     ptr <- mapViewOfFile fm fILE_MAP_READ 0 0
                     newForeignPtr c_UnmapViewOfFileFinaliser ptr
                 return (fp, fromIntegral $ bhfiSize fi)
-
--- | As mapFile, but returns ByteString
-mapFileBs :: FilePath -> IO ByteString
-mapFileBs p = do
-    (fp,i) <- mapFile p
-    return $ fromForeignPtr fp 0 i
 
 data MappedObject = MappedObject HANDLE HANDLE FileMapAccess
 
diff --git a/System/Win32/Types.hsc b/System/Win32/Types.hsc
--- a/System/Win32/Types.hsc
+++ b/System/Win32/Types.hsc
@@ -277,13 +277,13 @@
 
 -- Originally authored by Max Bolingbroke in the ansi-terminal library
 withHandleToHANDLE :: Handle -> (HANDLE -> IO a) -> IO a
-##if defined(__IO_MANAGER_WINIO__)
+#if defined(__IO_MANAGER_WINIO__)
 withHandleToHANDLE = withHandleToHANDLEPosix <!> withHandleToHANDLENative
-##else
+#else
 withHandleToHANDLE = withHandleToHANDLEPosix
-##endif
+#endif
 
-##if defined(__IO_MANAGER_WINIO__)
+#if defined(__IO_MANAGER_WINIO__)
 withHandleToHANDLENative :: Handle -> (HANDLE -> IO a) -> IO a
 withHandleToHANDLENative haskell_handle action =
     -- Create a stable pointer to the Handle. This prevents the garbage collector
@@ -293,7 +293,7 @@
         windows_handle <- handleToHANDLE haskell_handle
         -- Do what the user originally wanted
         action windows_handle
-##endif
+#endif
 
 withHandleToHANDLEPosix :: Handle -> (HANDLE -> IO a) -> IO a
 withHandleToHANDLEPosix haskell_handle action =
diff --git a/Win32.cabal b/Win32.cabal
--- a/Win32.cabal
+++ b/Win32.cabal
@@ -1,5 +1,5 @@
 name:           Win32
-version:        2.10.1.1
+version:        2.11.0.0
 license:        BSD3
 license-file:   LICENSE
 author:         Alastair Reid, shelarcy, Tamar Christina
@@ -28,7 +28,7 @@
         build-depends: unbuildable<0
         buildable: False
 
-    build-depends:      base >= 4.5 && < 5, bytestring, filepath
+    build-depends:      base >= 4.5 && < 5, filepath
     -- Black list hsc2hs 0.68.6 which is horribly broken.
     build-tool-depends: hsc2hs:hsc2hs > 0 && < 0.68.6 || > 0.68.6
     ghc-options:        -Wall -fno-warn-name-shadowing
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,9 @@
 # Changelog for [`Win32` package](http://hackage.haskell.org/package/Win32)
 
+## 2.11.0.0 January 2021
+
+* Remove function `mapFileBs`.
+
 ## 2.10.1.0 October 2020
 
 * Add `System.Win32.Event` module