diff --git a/lib/vagrant-lxc/driver.rb b/lib/vagrant-lxc/driver.rb
index ddaf4e3..104f279 100644
--- a/lib/vagrant-lxc/driver.rb
+++ b/lib/vagrant-lxc/driver.rb
@@ -275,7 +275,7 @@ def write_customizations(customizations)
       def write_config(contents)
         confpath = base_path.join('config').to_s
         begin
-          File.open(confpath, File::RDWR) do |file|
+          File.open(confpath, File::WRONLY|File::TRUNC) do |file|
             file.write contents
           end
         rescue