From ab431ed6a2e61df803e67b087fa26c785e8d3274 Mon Sep 17 00:00:00 2001
From: Steven Orvell <sorvell@google.com>
Date: Wed, 22 Jun 2016 09:20:53 -0700
Subject: [PATCH] Fixes #3730 and inspired by
 (https://github.com/Polymer/polymer/pull/3585)

---
 src/lib/dom-tree-api.html | 2 +-
 test/unit/polymer-dom.js  | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/lib/dom-tree-api.html b/src/lib/dom-tree-api.html
index ccf0dea031..37fa72cb26 100644
--- a/src/lib/dom-tree-api.html
+++ b/src/lib/dom-tree-api.html
@@ -215,7 +215,7 @@
         node.__dom.previousSibling.__dom.nextSibling = node;
       }
       // update node <-> ref_node
-      node.__dom.nextSibling = ref_node;
+      node.__dom.nextSibling = ref_node || null;
       if (node.__dom.nextSibling) {
         node.__dom.nextSibling.__dom.previousSibling = node;
       }
diff --git a/test/unit/polymer-dom.js b/test/unit/polymer-dom.js
index 02af167e9f..76bc284232 100644
--- a/test/unit/polymer-dom.js
+++ b/test/unit/polymer-dom.js
@@ -704,11 +704,13 @@ suite('Polymer.dom accessors', function() {
     var after = document.createElement('div');
     Polymer.dom(noDistribute).insertBefore(before, child);
     Polymer.dom(noDistribute).appendChild(after);
+    Polymer.dom.flush();
     assert.equal(Polymer.dom(noDistribute).firstChild, before, 'firstChild incorrect');
     assert.equal(Polymer.dom(noDistribute).lastChild, after, 'lastChild incorrect');
     assert.equal(Polymer.dom(before).nextSibling, child, 'nextSibling incorrect');
     assert.equal(Polymer.dom(child).nextSibling, after, 'nextSibling incorrect');
     assert.equal(Polymer.dom(after).previousSibling, child, 'previousSibling incorrect');
+    assert.equal(Polymer.dom(after).nextSibling, null, 'nextSibling incorrect');
     assert.equal(Polymer.dom(child).previousSibling, before, 'previousSibling incorrect');
   });
 
@@ -719,11 +721,13 @@ suite('Polymer.dom accessors', function() {
     var after = document.createElement('div');
     Polymer.dom(distribute).insertBefore(before, child);
     Polymer.dom(distribute).appendChild(after);
+    Polymer.dom.flush();
     assert.equal(Polymer.dom(distribute).firstChild, before, 'firstChild incorrect');
     assert.equal(Polymer.dom(distribute).lastChild, after, 'lastChild incorrect');
     assert.equal(Polymer.dom(before).nextSibling, child, 'nextSibling incorrect');
     assert.equal(Polymer.dom(child).nextSibling, after, 'nextSibling incorrect');
     assert.equal(Polymer.dom(after).previousSibling, child, 'previousSibling incorrect');
+    assert.equal(Polymer.dom(after).nextSibling, null, 'nextSibling incorrect');
     assert.equal(Polymer.dom(child).previousSibling, before, 'previousSibling incorrect');
   });