diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,10 @@
+filepath-bytestring (1.4.2.1.10) unstable; urgency=medium
+
+  * Depend on bytestring-0.11.2.0, and use it to implement encodeFilePath
+    and decodeFilePath, whose code was previously copied from it.
+
+ -- Joey Hess <id@joeyh.name>  Wed, 08 Dec 2021 18:55:24 -0400
+
 filepath-bytestring (1.4.2.1.9) unstable; urgency=medium
 
   * Relax bounds to allow base 4.16 (ghc 9.2).
diff --git a/System/FilePath/Internal.hs b/System/FilePath/Internal.hs
--- a/System/FilePath/Internal.hs
+++ b/System/FilePath/Internal.hs
@@ -136,15 +136,12 @@
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as B
 import qualified Data.ByteString.Char8 as B8
-import Data.ByteString.Unsafe (unsafePackMallocCStringLen)
 import Data.Char(ord, chr, toUpper, toLower, isAsciiLower, isAsciiUpper)
 import Data.Maybe(isJust)
 import Data.Word(Word8)
 #ifdef mingw32_HOST_OS
 import qualified Data.ByteString.UTF8 as UTF8
 #else
-import qualified GHC.Foreign as GHC
-import qualified GHC.IO.Encoding as Encoding
 import System.IO.Unsafe (unsafePerformIO)
 #endif
 import System.Environment (getEnv)
@@ -171,13 +168,14 @@
 -- (see `Encoding.getFileSystemEncoding`).
 --
 -- When run on Windows, this encodes as UTF-8.
+-- 
+-- the implementation of this function assumes that the
+-- filesystem encoding will not be changed while the program is running.
 encodeFilePath :: FilePath -> RawFilePath
 #ifdef mingw32_HOST_OS
 encodeFilePath = UTF8.fromString
 #else
-encodeFilePath f = unsafePerformIO $ do
-	enc <- Encoding.getFileSystemEncoding
-	GHC.newCStringLen enc f >>= unsafePackMallocCStringLen
+encodeFilePath = unsafePerformIO . B.fromFilePath
 #endif
 
 -- | Convert from RawFilePath to FilePath
@@ -186,14 +184,15 @@
 -- (see `Encoding.getFileSystemEncoding`).
 --
 -- When run on Windows, this decodes UTF-8.
+
+-- The implementation of this function assumes that the
+-- filesystem encoding will not be changed while the program is running.
 decodeFilePath :: RawFilePath -> FilePath
 #ifdef mingw32_HOST_OS
 decodeFilePath = UTF8.toString
 #else
 {-# NOINLINE decodeFilePath #-}
-decodeFilePath f = unsafePerformIO $ do
-	enc <- Encoding.getFileSystemEncoding
-	B.useAsCStringLen f (GHC.peekCStringLen enc)
+decodeFilePath = unsafePerformIO . B.toFilePath
 #endif
 
 ---------------------------------------------------------------------
diff --git a/filepath-bytestring.cabal b/filepath-bytestring.cabal
--- a/filepath-bytestring.cabal
+++ b/filepath-bytestring.cabal
@@ -1,6 +1,6 @@
 cabal-version: 1.18
 name:           filepath-bytestring
-version:        1.4.2.1.9
+version:        1.4.2.1.10
 -- NOTE: Don't forget to update CHANGELOG and the filepath dependency below
 license:        BSD3
 license-file:   LICENSE
@@ -50,7 +50,7 @@
 
     build-depends:
         base >= 4 && < 4.17,
-        bytestring
+        bytestring >= 0.11.2.0
     if os(Windows)
         build-depends: utf8-string
     else
@@ -71,7 +71,7 @@
     build-depends:
         filepath-bytestring,
         base,
-        bytestring,
+        bytestring >= 0.11.2.0,
         QuickCheck >= 2.7 && < 2.15,
 	-- Versions of filepath that are equvilant to this
 	-- library, for quickcheck equivilance tests.