diff --git a/lib/nerdtree/creator.vim b/lib/nerdtree/creator.vim
index a893c17..5eac168 100644
--- a/lib/nerdtree/creator.vim
+++ b/lib/nerdtree/creator.vim
@@ -96,8 +96,7 @@ function! s:Creator.createWindowTree(dir)
 
     "we need a unique name for each window tree buffer to ensure they are
     "all independent
-    let t:NERDTreeBufName = self._nextBufferName()
-    exec g:NERDTreeCreatePrefix . " edit " . t:NERDTreeBufName
+    exec g:NERDTreeCreatePrefix . " edit " . self._nextBufferName()
 
     call self._createNERDTree(path, "window")
     let b:NERDTree._previousBuf = bufnr(previousBuf)
diff --git a/lib/nerdtree/nerdtree.vim b/lib/nerdtree/nerdtree.vim
index c1ce5ed..e5ba0b5 100644
--- a/lib/nerdtree/nerdtree.vim
+++ b/lib/nerdtree/nerdtree.vim
@@ -153,7 +153,7 @@ endfunction
 
 "FUNCTION: s:NERDTree.IsOpen() {{{1
 function! s:NERDTree.IsOpen()
-    return s:NERDTree.GetWinNum() != -1
+    return s:NERDTree.GetWinNum() != -1 || bufname('%') =~# '^' . g:NERDTreeCreator.BufNamePrefix() . '\d\+$'
 endfunction
 
 "FUNCTION: s:NERDTree.isTabTree() {{{1