diff --git a/lib/appenders/smtp.js b/lib/appenders/smtp.js
index 6fa4b66..1ec1a0f 100644
--- a/lib/appenders/smtp.js
+++ b/lib/appenders/smtp.js
@@ -2,6 +2,7 @@
 var layouts = require("../layouts")
 , mailer = require("nodemailer")
 , os = require('os')
+, async = require('async')
 , unsentCount = 0
 , shutdownTimeout;