diff --git a/plugin/NERD_tree.vim b/plugin/NERD_tree.vim
index 667b896..20a44f4 100644
--- a/plugin/NERD_tree.vim
+++ b/plugin/NERD_tree.vim
@@ -39,7 +39,7 @@ set cpo&vim
 "1 if the var is set, 0 otherwise
 function! s:initVariable(var, value)
     if !exists(a:var)
-        exec 'let ' . a:var . ' = ' . "'" . a:value . "'"
+        exec 'let ' . a:var . ' = ' . "'" . substitute(a:value, "'", "''", "g") . "'"
         return 1
     endif
     return 0