diff --git a/lib/nerdtree/path.vim b/lib/nerdtree/path.vim
index 71be5f5..0aa592e 100644
--- a/lib/nerdtree/path.vim
+++ b/lib/nerdtree/path.vim
@@ -392,17 +392,19 @@ endfunction
 " FUNCTION: Path.getSortKey() {{{1
 " returns a key used in compare function for sorting
 function! s:Path.getSortKey()
-    let path = self.getLastPathComponent(1)
-    if !g:NERDTreeSortHiddenFirst
-        let path = substitute(path, '^[._]', '', '')
-    endif
-    if !g:NERDTreeCaseSensitiveSort
-        let path = tolower(path)
-    endif
-    if !g:NERDTreeNaturalSort
-        let self._sortKey = [self.getSortOrderIndex(), path]
-    else
-        let self._sortKey = [self.getSortOrderIndex()] + self._splitChunks(path)
+    if !exists("self._sortKey") || g:NERDTreeSortOrder !=# g:NERDTreeOldSortOrder
+        let path = self.getLastPathComponent(1)
+        if !g:NERDTreeSortHiddenFirst
+            let path = substitute(path, '^[._]', '', '')
+        endif
+        if !g:NERDTreeCaseSensitiveSort
+            let path = tolower(path)
+        endif
+        if !g:NERDTreeNaturalSort
+            let self._sortKey = [self.getSortOrderIndex(), path]
+        else
+            let self._sortKey = [self.getSortOrderIndex()] + self._splitChunks(path)
+        endif
     endif
 
     return self._sortKey
diff --git a/lib/nerdtree/tree_dir_node.vim b/lib/nerdtree/tree_dir_node.vim
index 2f62ec3..30db853 100644
--- a/lib/nerdtree/tree_dir_node.vim
+++ b/lib/nerdtree/tree_dir_node.vim
@@ -612,6 +612,7 @@ function! s:TreeDirNode.sortChildren()
     endif
     let CompareFunc = function("nerdtree#compareNodesBySortKey")
     call sort(self.children, CompareFunc)
+    let g:NERDTreeOldSortOrder = g:NERDTreeSortOrder
 endfunction
 
 " FUNCTION: TreeDirNode.toggleOpen([options]) {{{1
diff --git a/plugin/NERD_tree.vim b/plugin/NERD_tree.vim
index a8af089..71d719a 100644
--- a/plugin/NERD_tree.vim
+++ b/plugin/NERD_tree.vim
@@ -82,6 +82,7 @@ call s:initVariable("g:NERDTreeCascadeSingleChildDir", 1)
 if !exists("g:NERDTreeSortOrder")
     let g:NERDTreeSortOrder = ['\/$', '*', '\.swp$',  '\.bak$', '\~$']
 endif
+let g:NERDTreeOldSortOrder = []
 
 call s:initVariable("g:NERDTreeGlyphReadOnly", "RO")