diff --git a/plugin/NERD_tree.vim b/plugin/NERD_tree.vim
index fdb0d0d..632042d 100644
--- a/plugin/NERD_tree.vim
+++ b/plugin/NERD_tree.vim
@@ -3546,7 +3546,7 @@ function! s:closeCurrentDir()
     endif
 
     let parent = treenode.parent
-    if parent.isRoot()
+    if parent ==# {} || parent.isRoot()
         call s:echo("cannot close tree root")
     else
         call treenode.parent.close()