diff --git a/JavaScript/6-doubly-proto.js b/JavaScript/6-doubly-proto.js
index 62e5a21..d2324aa 100644
--- a/JavaScript/6-doubly-proto.js
+++ b/JavaScript/6-doubly-proto.js
@@ -20,6 +20,7 @@ LinkedList.prototype.pop = function() {
   if (this.length === 0) return null;
   const node = this.last;
   this.last = node.prev;
+  this.last.next = null;
   node.list = null;
   node.prev = null;
   node.next = null;