diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## Path IO 1.4.1
+
+* Fixed a bug in `walkDirRel` that resulted in `NotAProperPrefix` exception
+  every time the function was called.
+
 ## Path IO 1.4.0
 
 * Added relative versions of some actions: `listDirRel`, `listDirRecurRel`,
diff --git a/Path/IO.hs b/Path/IO.hs
--- a/Path/IO.hs
+++ b/Path/IO.hs
@@ -14,6 +14,7 @@
 
 {-# LANGUAGE CPP               #-}
 {-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE TemplateHaskell   #-}
 {-# LANGUAGE TupleSections     #-}
 {-# LANGUAGE TypeFamilies      #-}
 
@@ -126,9 +127,6 @@
 #if MIN_VERSION_directory(1,2,3)
 import System.Directory (XdgDirectory)
 #endif
-#if !MIN_VERSION_base(4,8,0)
-import Data.Monoid (Monoid)
-#endif
 
 ----------------------------------------------------------------------------
 -- Actions on directories
@@ -564,8 +562,9 @@
         stripDir topdir
 #endif
       handler curdir subdirs files = do
-        -- These should not ever fail.
-        curdirRel  <- stripTopdir curdir
+        curdirRel  <- if curdir == topdir
+          then return $(mkRelDir ".")
+          else stripTopdir curdir
         subdirsRel <- mapM stripTopdir subdirs
         filesRel   <- mapM stripTopdir files
         action     <- handler' curdirRel subdirsRel filesRel
diff --git a/path-io.cabal b/path-io.cabal
--- a/path-io.cabal
+++ b/path-io.cabal
@@ -1,7 +1,7 @@
 name:                 path-io
-version:              1.4.0
+version:              1.4.1
 cabal-version:        1.18
-tested-with:          GHC==7.10.3, GHC==8.0.2, GHC==8.2.2, GHC==8.4.3
+tested-with:          GHC==7.10.3, GHC==8.0.2, GHC==8.2.2, GHC==8.4.4, GHC==8.6.3
 license:              BSD3
 license-file:         LICENSE.md
 author:               Mark Karpov <markkarpov92@gmail.com>
diff --git a/tests/Main.hs b/tests/Main.hs
--- a/tests/Main.hs
+++ b/tests/Main.hs
@@ -36,6 +36,7 @@
   describe "getCurrentDir"    getCurrentDirSpec
   describe "setCurrentDir"    setCurrentDirSpec
   describe "withCurrentDir"   withCurrentDirSpec
+  describe "walkDirRel"       walkDirRelSpec
 #ifndef mingw32_HOST_OS
   -- NOTE We can't quite test this on Windows as well, because the
   -- environmental variables HOME and TMPDIR do not exist there.
@@ -159,6 +160,15 @@
   withCurrentDir dir $
     getCurrentDir `shouldReturn` dir
   getCurrentDir `shouldNotReturn` dir
+
+walkDirRelSpec :: SpecWith (Path Abs Dir)
+walkDirRelSpec = it "does not throw exceptions" $ \dir -> do
+  let handler curdir subdirs files = do
+        curdir `shouldBe` $(mkRelDir ".")
+        subdirs `shouldBe` []
+        files `shouldBe` []
+        return WalkFinish
+  walkDirRel handler dir
 
 getHomeDirSpec :: SpecWith (Path Abs Dir)
 getHomeDirSpec =