diff --git a/lib/Connection.js b/lib/Connection.js
index 7e2046e..3efcadc 100644
--- a/lib/Connection.js
+++ b/lib/Connection.js
@@ -1474,6 +1474,9 @@ Connection.prototype._resUntagged = function(info) {
 Connection.prototype._resTagged = function(info) {
   var req = this._curReq, err;
 
+  if (!req)
+    return;
+
   this._curReq = undefined;
 
   if (info.type === 'no' || info.type === 'bad') {