diff --git a/README.md b/README.md
index 1d7678b..52c7c36 100644
--- a/README.md
+++ b/README.md
@@ -458,6 +458,7 @@ As you see, z.lua is the fastest one and requires less resource.
 
 ## History
 
+- 1.5.11 (2019-03-02): fixed: os.path.isdir not work for symbol link folders.
 - 1.5.10 (2019-03-01): Prevent writing file racing.
 - 1.5.9 (2019-02-25): `z -b` should not match current directory (close #56).
 - 1.5.8 (2019-02-21): new `$_ZL_FZF_HEIGHT` to control `--height` parameter in fzf.
diff --git a/z.lua b/z.lua
index 5499a3e..6a4e2a0 100755
--- a/z.lua
+++ b/z.lua
@@ -4,7 +4,7 @@
 -- z.lua - a cd command that learns, by skywind 2018, 2019
 -- Licensed under MIT license.
 --
--- Version 1.5.10, Last Modified: 2019/03/01 13:08
+-- Version 1.5.11, Last Modified: 2019/03/02 11:37
 --
 -- * 10x faster than fasd and autojump, 3x faster than z.sh
 -- * available for posix shells: bash, zsh, sh, ash, dash, busybox
@@ -427,8 +427,6 @@ function os.path.isdir(pathname)
 	elseif windows then
 		if pathname == '\\' then
 			return true
-		elseif pathname:match('^%a:[/\\]$') then
-			return true
 		end
 	end
 	local name = pathname
@@ -453,6 +451,12 @@ function os.path.exists(name)
 				io.close(f)
 				return true
 			end
+		elseif name:sub(-1) == '/' and code == 20 and (not windows) then
+			local test = name .. '.'
+			ok, err, code = os.rename(test, test)
+			if code == 16 or code == 13 then
+				return true
+			end
 		end
 		return false
 	end