diff --git a/README.md b/README.md
index 0016f9b..db2d151 100644
--- a/README.md
+++ b/README.md
@@ -137,8 +137,11 @@ z -b foo    # cd to the parent directory starting with foo
 
 - Windows WSL-1:
 
-  - Install `lua-filesystem` module.
-  - Initialize z.lua as in Linux.
+  Install `lua-filesystem` module before init z.lua:
+        
+        sudo apt-get install lua-filesystem
+
+  This module is required due to a wsl-1 [defect](https://github.com/microsoft/WSL/issues/5505).
 
 
 
diff --git a/z.lua b/z.lua
index 7bc42fc..378a788 100755
--- a/z.lua
+++ b/z.lua
@@ -1,10 +1,10 @@
 #! /usr/bin/env lua
 --=====================================================================
 --
--- z.lua - a cd command that learns, by skywind 2018, 2019, 2020
+-- z.lua - a cd command that learns, by skywind 2018, 2019, 2020, 2021
 -- Licensed under MIT license.
 --
--- Version 1.8.12, Last Modified: 2020/12/31 02:05
+-- Version 1.8.12, Last Modified: 2021/02/15 00:05
 --
 -- * 10x faster than fasd and autojump, 3x faster than z.sh
 -- * available for posix shells: bash, zsh, sh, ash, dash, busybox
@@ -64,6 +64,10 @@
 --     * Add cmder/vendor to %PATH%
 --     * Ensure that "lua" can be called in %PATH%
 --
+-- Windows WSL-1:
+--     * Install lua-filesystem module before init z.lua:
+--         sudo apt-get install lua-filesystem
+--
 -- Configure (optional):
 --   set $_ZL_CMD in .bashrc/.zshrc to change the command (default z).
 --   set $_ZL_DATA in .bashrc/.zshrc to change the datafile (default ~/.zlua).
@@ -2744,4 +2748,5 @@ if not pcall(debug.getlocal, 4, 1) then
 	end
 end
 
+-- vim: set ts=4 sw=4 tw=0 noet :