diff --git a/README.markdown b/README.markdown
index fd8655c..66e8896 100644
--- a/README.markdown
+++ b/README.markdown
@@ -106,7 +106,7 @@ Stick this in your vimrc to open NERDTree with `Ctrl+n` (you can set whatever ke
 
 Stick this in your vimrc:
 
-    autocmd bufenter * if (winnr("$") == 1 && exists("b:NERDTreeType") && b:NERDTreeType == "primary") | q | endif
+    autocmd bufenter * if (winnr("$") == 1 && exists("b:NERDTree") && b:NERDTree.isTabTree()) | q | endif
 
 > Can I have different highlighting for different file extensions?
 
diff --git a/autoload/nerdtree/ui_glue.vim b/autoload/nerdtree/ui_glue.vim
index 50298d2..5e08a0d 100644
--- a/autoload/nerdtree/ui_glue.vim
+++ b/autoload/nerdtree/ui_glue.vim
@@ -208,7 +208,7 @@ endfunction
 " FUNCTION: s:closeTreeWindow() {{{1
 " close the tree window
 function! s:closeTreeWindow()
-    if b:NERDTreeType ==# "window" && b:NERDTreePreviousBuf != -1
+    if b:NERDTree.isWinTree() && b:NERDTreePreviousBuf != -1
         exec "buffer " . b:NERDTreePreviousBuf
     else
         if winnr("$") > 1
diff --git a/lib/nerdtree/creator.vim b/lib/nerdtree/creator.vim
index 842311c..87407d7 100644
--- a/lib/nerdtree/creator.vim
+++ b/lib/nerdtree/creator.vim
@@ -42,7 +42,7 @@ endfunction
 "name: the name of a bookmark or a directory
 function! s:Creator.createTabTree(name)
     let path = self._pathForString(a:name)
-    
+
     "abort if exception was thrown (bookmark/dir doesn't exist)
     if empty(path)
         return
@@ -66,8 +66,7 @@ function! s:Creator.createTabTree(name)
     endif
 
     call self._createTreeWin()
-    call self._createNERDTree(path)
-    let b:NERDTreeType = "tab"
+    call self._createNERDTree(path, "tab")
     let b:treeShowHelp = 0
     let b:NERDTreeIgnoreEnabled = 1
     let b:NERDTreeShowFiles = g:NERDTreeShowFiles
@@ -105,9 +104,8 @@ function! s:Creator.createWindowTree(dir)
     exec "silent edit " . self._nextBufferName()
 
     let b:NERDTreePreviousBuf = bufnr(previousBuf)
-    call self._createNERDTree(path)
+    call self._createNERDTree(path, "window")
     call self._setCommonBufOptions()
-    let b:NERDTreeType = "window"
 
     call b:NERDTree.render()
 
@@ -115,8 +113,8 @@ function! s:Creator.createWindowTree(dir)
 endfunction
 
 " FUNCTION: s:Creator._createNERDTree(path) {{{1
-function! s:Creator._createNERDTree(path)
-    let b:NERDTree = g:NERDTree.New(a:path)
+function! s:Creator._createNERDTree(path, type)
+    let b:NERDTree = g:NERDTree.New(a:path, a:type)
     "TODO: This is kept for compatability only since many things use
     "b:NERDTreeRoot instead of the new NERDTree.root
     "Remove this one day
diff --git a/lib/nerdtree/nerdtree.vim b/lib/nerdtree/nerdtree.vim
index 46e7129..801282e 100644
--- a/lib/nerdtree/nerdtree.vim
+++ b/lib/nerdtree/nerdtree.vim
@@ -105,6 +105,16 @@ function! s:NERDTree.IsOpen()
     return s:NERDTree.GetWinNum() != -1
 endfunction
 
+"FUNCTION: s:NERDTree.isTabTree() {{{1
+function! s:NERDTree.isTabTree()
+    return self._type == "tab"
+endfunction
+
+"FUNCTION: s:NERDTree.isWinTree() {{{1
+function! s:NERDTree.isWinTree()
+    return self._type == "window"
+endfunction
+
 "FUNCTION: s:NERDTree.MustBeOpen() {{{1
 function! s:NERDTree.MustBeOpen()
     if !s:NERDTree.IsOpen()
@@ -113,10 +123,11 @@ function! s:NERDTree.MustBeOpen()
 endfunction
 
 "FUNCTION: s:NERDTree.New() {{{1
-function! s:NERDTree.New(path)
+function! s:NERDTree.New(path, type)
     let newObj = copy(self)
     let newObj.ui = g:NERDTreeUI.New(newObj)
     let newObj.root = g:NERDTreeDirNode.New(a:path)
+    let newObj._type = a:type
 
     return newObj
 endfunction
diff --git a/lib/nerdtree/opener.vim b/lib/nerdtree/opener.vim
index 6740bd4..0f8a005 100644
--- a/lib/nerdtree/opener.vim
+++ b/lib/nerdtree/opener.vim
@@ -64,7 +64,7 @@ endfunction
 
 "FUNCTION: Opener._gotoTargetWin() {{{1
 function! s:Opener._gotoTargetWin()
-    if b:NERDTreeType ==# "window"
+    if b:NERDTree.isWinTree()
         if self._where == 'v'
             vsplit
         elseif self._where == 'h'
@@ -149,7 +149,7 @@ function! s:Opener.New(path, opts)
 
     let newObj._keepopen = nerdtree#has_opt(a:opts, 'keepopen')
     let newObj._where = has_key(a:opts, 'where') ? a:opts['where'] : ''
-    let newObj._treetype = b:NERDTreeType
+    let newObj._nerdtree = b:NERDTree
     call newObj._saveCursorPos()
 
     return newObj
@@ -248,7 +248,7 @@ function! s:Opener._openFile()
 
     call self._gotoTargetWin()
 
-    if self._treetype ==# "window"
+    if self._nerdtree.isWinTree()
         call self._path.edit()
     else
         call self._path.edit()
@@ -262,7 +262,7 @@ endfunction
 
 "FUNCTION: Opener._openDirectory(node) {{{1
 function! s:Opener._openDirectory(node)
-    if self._treetype ==# "window"
+    if self._nerdtree.isWinTree()
         call self._gotoTargetWin()
         call g:NERDTreeCreator.CreateWindow(a:node.path.str())
     else
diff --git a/lib/nerdtree/ui.vim b/lib/nerdtree/ui.vim
index 1e18858..8e18805 100644
--- a/lib/nerdtree/ui.vim
+++ b/lib/nerdtree/ui.vim
@@ -27,12 +27,12 @@ function! s:UI._dumpHelp()
         let @h=@h."\" File node mappings~\n"
         let @h=@h."\" ". (g:NERDTreeMouseMode ==# 3 ? "single" : "double") ."-click,\n"
         let @h=@h."\" <CR>,\n"
-        if b:NERDTreeType ==# "tab"
+        if b:NERDTree.isTabTree()
             let @h=@h."\" ". g:NERDTreeMapActivateNode .": open in prev window\n"
         else
             let @h=@h."\" ". g:NERDTreeMapActivateNode .": open in current window\n"
         endif
-        if b:NERDTreeType ==# "tab"
+        if b:NERDTree.isTabTree()
             let @h=@h."\" ". g:NERDTreeMapPreview .": preview\n"
         endif
         let @h=@h."\" ". g:NERDTreeMapOpenInTab.": open in new tab\n"