diff --git a/plugins/synced_folders/rsync/helper.rb b/plugins/synced_folders/rsync/helper.rb
index 557bd83d2..c190cf3c1 100644
--- a/plugins/synced_folders/rsync/helper.rb
+++ b/plugins/synced_folders/rsync/helper.rb
@@ -1,5 +1,6 @@
 require "ipaddr"
 require "shellwords"
+require "tmpdir"
 
 require "vagrant/util/platform"
 require "vagrant/util/subprocess"