diff --git a/System/FilePath/Internal.hs b/System/FilePath/Internal.hs
--- a/System/FilePath/Internal.hs
+++ b/System/FilePath/Internal.hs
@@ -120,7 +120,7 @@
 #ifndef OS_PATH
 import Data.String (fromString)
 import System.Environment(getEnv)
-import Prelude (String, map, FilePath, Eq, IO, id, last, init, reverse, dropWhile, null, break, takeWhile, take, all, elem, any, head, tail, span)
+import Prelude (String, map, FilePath, Eq, IO, id, last, init, reverse, dropWhile, null, break, takeWhile, take, all, elem, any, span)
 import Data.Char(toLower, toUpper, isAsciiLower, isAsciiUpper)
 import Data.List(stripPrefix, isSuffixOf, uncons)
 #define CHAR Char
@@ -672,9 +672,7 @@
 
 
 hasLeadingPathSeparator :: FILEPATH -> Bool
-hasLeadingPathSeparator x
-  | null x = False
-  | otherwise = isPathSeparator $ head x
+hasLeadingPathSeparator = maybe False (isPathSeparator . fst) . uncons
 
 
 -- | Add a trailing file path separator if one is not already present.
@@ -901,11 +899,21 @@
       where (a, b) = break isPathSeparator $ dropWhile isPathSeparator x
 
     -- on windows, need to drop '/' which is kind of absolute, but not a drive
-    dropAbs x | not (null x) && isPathSeparator (head x) && not (hasDrive x) = tail x
-    dropAbs x = dropDrive x
+    dropAbs x
+      | Just (hd, tl) <- uncons x
+      , isPathSeparator hd
+      , not (hasDrive x)
+      = tl
+      | otherwise
+      = dropDrive x
 
-    takeAbs x | not (null x) && isPathSeparator (head x) && not (hasDrive x) = singleton pathSeparator
-    takeAbs x = map (\y -> if isPathSeparator y then pathSeparator else toLower y) $ takeDrive x
+    takeAbs x
+      | Just (hd, _) <- uncons x
+      , isPathSeparator hd
+      , not (hasDrive x)
+      = singleton pathSeparator
+      | otherwise
+      = map (\y -> if isPathSeparator y then pathSeparator else toLower y) $ takeDrive x
 
 -- | Normalise a file
 --
@@ -955,7 +963,7 @@
            then singleton _period
            else joinDrive d p
 
-    addPathSeparator = isDirPath filepath
+    addPathSeparator = isDirPath pth
       && not (hasTrailingPathSeparator result)
       && not (isRelativeDrive drv)
 
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -2,10 +2,18 @@
 
 _Note: below all `FilePath` values are unquoted, so `\\` really means two backslashes._
 
+## 1.4.100.1 *Feb 2023*
+
+* Fix regression in `System.FilePath.Windows.normalise` wrt [#187](https://github.com/haskell/filepath/issues/187)
+* Fix tests on GHC 9.4.4
+* Avoid head and tail
+
 ## 1.4.100.0 *July 2022*
 
 Implementation of the [Abstract FilePath Proposal](https://gitlab.haskell.org/ghc/ghc/-/wikis/proposal/abstract-file-path)
 in user-space as a separate type.
+
+Introduction to the new API is explained [in this blog post](https://hasufell.github.io/posts/2022-06-29-fixing-haskell-filepaths.html).
 
 ## 1.4.2.2 *Dec 2021*
 
diff --git a/filepath.cabal b/filepath.cabal
--- a/filepath.cabal
+++ b/filepath.cabal
@@ -1,6 +1,6 @@
 cabal-version:      2.2
 name:               filepath
-version:            1.4.100.0
+version:            1.4.100.1
 
 -- NOTE: Don't forget to update ./changelog.md
 license:            BSD-3-Clause
@@ -8,9 +8,9 @@
 author:             Neil Mitchell <ndmitchell@gmail.com>
 maintainer:         Julian Ospald <hasufell@posteo.de>
 copyright:          Neil Mitchell 2005-2020, Julain Ospald 2021-2022
-bug-reports:        https://gitlab.haskell.org/haskell/filepath/-/issues
+bug-reports:        https://github.com/haskell/filepath/issues
 homepage:
-  https://gitlab.haskell.org/haskell/filepath/-/blob/master/README.md
+  https://github.com/haskell/filepath/blob/master/README.md
 
 category:           System
 build-type:         Simple
@@ -44,6 +44,10 @@
   .
   "System.OsString" is like "System.OsPath", but more general purpose. Refer to the documentation of
   those modules for more information.
+  .
+  An introduction into the new API can be found in this
+  <https://hasufell.github.io/posts/2022-06-29-fixing-haskell-filepaths.html blog post>.
+  Code examples for the new API can be found <https://github.com/hasufell/filepath-examples here>.
 
 extra-source-files:
   Generate.hs
@@ -65,7 +69,7 @@
 
 source-repository head
   type:     git
-  location: https://gitlab.haskell.org/haskell/filepath
+  location: https://github.com/haskell/filepath
 
 library
   exposed-modules:
@@ -99,7 +103,7 @@
 
   default-language: Haskell2010
   build-depends:
-    , base              >=4.9      && <4.18
+    , base              >=4.9      && <4.19
     , bytestring        >=0.11.3.0
     , deepseq
     , exceptions
diff --git a/tests/abstract-filepath/EncodingSpec.hs b/tests/abstract-filepath/EncodingSpec.hs
--- a/tests/abstract-filepath/EncodingSpec.hs
+++ b/tests/abstract-filepath/EncodingSpec.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE ViewPatterns #-}
 {-# LANGUAGE TypeApplications #-}
@@ -38,7 +39,11 @@
       let str = [toEnum 55296, toEnum 55297]
           encoded = encodeWithTE utf16le str
           decoded = decodeWithTE utf16le =<< encoded
+#if __GLASGOW_HASKELL__ >= 904
+      in decoded === Left (EncodingError ("recoverEncode: invalid argument (cannot encode character " <> show (head str) <> ")") Nothing))
+#else
       in decoded === Left (EncodingError "recoverEncode: invalid argument (invalid character)" Nothing))
+#endif
   , ("ucs2 handles invalid surrogate pairs",
      property $
       let str = [toEnum 55296, toEnum 55297]
@@ -64,7 +69,11 @@
       let str = [toEnum 0xDFF0, toEnum 0xDFF2]
           encoded = encodeWithTE (mkUTF8 RoundtripFailure) str
           decoded = decodeWithTE (mkUTF8 RoundtripFailure) =<< encoded
+#if __GLASGOW_HASKELL__ >= 904
+      in decoded === Left (EncodingError ("recoverEncode: invalid argument (cannot encode character " <> show (head str) <> ")") Nothing))
+#else
       in decoded === Left (EncodingError "recoverEncode: invalid argument (invalid character)" Nothing))
+#endif
 
   , ("cannot roundtrip arbitrary bytes through utf-16 (with RoundtripFailure)",
      property $