diff --git a/server/lib/builtin-zone-mta.js b/server/lib/builtin-zone-mta.js
index ded3b5c6..e867792b 100644
--- a/server/lib/builtin-zone-mta.js
+++ b/server/lib/builtin-zone-mta.js
@@ -7,6 +7,7 @@ const path = require('path');
 const fs = require('fs-extra');
 const crypto = require('crypto');
 const bluebird = require('bluebird');
+const os = require('os');
 
 let zoneMtaProcess = null;