diff --git a/lib/server.js b/lib/server.js
index 81ca446..ae43815 100644
--- a/lib/server.js
+++ b/lib/server.js
@@ -46,7 +46,9 @@ module.exports = function(options) {
             logger.warn(format('Forcefully stopping server on %s:%d', config.host, config.port))
             server.destroy(cb)
         }, duration(config.shutdown.delay))
-        destroy.unref()
+        if(destroy instanceof Object){
+            destroy.unref()
+        }
     }
 
     function close(cb) {