diff --git a/vim/vimrc b/vim/vimrc
index c627991..0e75436 100644
--- a/vim/vimrc
+++ b/vim/vimrc
@@ -43,10 +43,10 @@ if has('nvim')
 endif
 
 if has("persistent_undo")
-    if !isdirectory("$HOME" . "/.undodir")
-        call mkdir("$HOME" . "/.undodir", "p", 0770)
+    if !isdirectory($HOME . "/.undodir")
+        call mkdir($HOME . "/.undodir", "p", 0770)
     endif
-    set undodir="$HOME" . "/.undodir//"
+    set undodir=~/.undodir/
     set undofile
     augroup undodir
         autocmd!