diff --git a/index.js b/index.js
index cfe377c..d516322 100644
--- a/index.js
+++ b/index.js
@@ -45,7 +45,9 @@ function release (client, err) {
     }, this.options.idleTimeoutMillis)
   }
 
-  this._idle.push(new IdleItem(client, tid))
+  if (this._clients.indexOf(client) > -1) {
+    this._idle.push(new IdleItem(client, tid))
+  }
   this._pulseQueue()
 }