diff --git a/lib/imap.js b/lib/imap.js
index b68669c..768d34b 100644
--- a/lib/imap.js
+++ b/lib/imap.js
@@ -1504,6 +1504,9 @@ ImapConnection.prototype._noop = function() {
 };
 
 ImapConnection.prototype._send = function(cmdstr, cb, bypass) {
+  if (!this._state.conn.writable)
+    return;
+
   if (cmdstr !== undefined && !bypass) {
     this._state.requests.push({
       cmd: cmdstr.match(RE_CMD)[1],