diff --git a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js
index bfd2125..6ea48ac 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js
@@ -388,8 +388,8 @@
       return null;
     }
 
-    const threadGroupEl =
-        document.createElement('gr-diff-comment-thread-group');
+    const threadGroupEl = document.createElement('div');
+    threadGroupEl.className = 'thread-group';
     for (const threadEl of threadElsForGroup) {
       Polymer.dom(threadGroupEl).appendChild(threadEl);
     }
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-comment-thread-group/gr-diff-comment-thread-group.html b/polygerrit-ui/app/elements/diff/gr-diff-comment-thread-group/gr-diff-comment-thread-group.html
deleted file mode 100644
index 1f77c0d..0000000
--- a/polygerrit-ui/app/elements/diff/gr-diff-comment-thread-group/gr-diff-comment-thread-group.html
+++ /dev/null
@@ -1,39 +0,0 @@
-<!--
-@license
-Copyright (C) 2017 The Android Open Source Project
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
--->
-
-<link rel="import" href="../../../bower_components/polymer/polymer.html">
-<link rel="import" href="../gr-diff-comment-thread/gr-diff-comment-thread.html">
-<link rel="import" href="../../../styles/shared-styles.html">
-
-<dom-module id="gr-diff-comment-thread-group">
-  <template>
-    <style include="shared-styles">
-      :host {
-        display: block;
-        max-width: var(--content-width, 80ch);
-        white-space: normal;
-      }
-      div ::slotted(*) + div ::slotted(*) {
-        margin-top: .2em;
-      }
-    </style>
-    <div>
-      <slot class="comment-thread"></slot>
-    </div>
-  </template>
-  <script src="gr-diff-comment-thread-group.js"></script>
-</dom-module>
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-comment-thread-group/gr-diff-comment-thread-group.js b/polygerrit-ui/app/elements/diff/gr-diff-comment-thread-group/gr-diff-comment-thread-group.js
deleted file mode 100644
index 0321826..0000000
--- a/polygerrit-ui/app/elements/diff/gr-diff-comment-thread-group/gr-diff-comment-thread-group.js
+++ /dev/null
@@ -1,26 +0,0 @@
-/**
- * @license
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-(function() {
-  'use strict';
-
-  Polymer({
-    is: 'gr-diff-comment-thread-group',
-
-    properties: {
-    },
-  });
-})();
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-comment-thread-group/gr-diff-comment-thread-group_test.html b/polygerrit-ui/app/elements/diff/gr-diff-comment-thread-group/gr-diff-comment-thread-group_test.html
deleted file mode 100644
index 8219d1b..0000000
--- a/polygerrit-ui/app/elements/diff/gr-diff-comment-thread-group/gr-diff-comment-thread-group_test.html
+++ /dev/null
@@ -1,49 +0,0 @@
-<!DOCTYPE html>
-<!--
-@license
-Copyright (C) 2017 The Android Open Source Project
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
--->
-
-<meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
-<title>gr-diff-comment-thread-group</title>
-
-<script src="../../../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
-<script src="../../../bower_components/web-component-tester/browser.js"></script>
-<link rel="import" href="../../../test/common-test-setup.html"/>
-<script src="../../../scripts/util.js"></script>
-
-<link rel="import" href="gr-diff-comment-thread-group.html">
-
-<script>void(0);</script>
-
-<test-fixture id="basic">
-  <template>
-    <gr-diff-comment-thread-group></gr-diff-comment-thread-group>
-  </template>
-</test-fixture>
-
-<script>
-  suite('gr-diff-comment-thread-group tests', () => {
-    let sandbox;
-
-    setup(() => {
-      sandbox = sinon.sandbox.create();
-    });
-
-    teardown(() => {
-      sandbox.restore();
-    });
-  });
-</script>
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html
index b258455..80ca01d 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.html
@@ -36,6 +36,11 @@
       :host(.no-left) .sideBySide ::content .right:not([data-value]) + td {
         display: none;
       }
+      ::slotted(*) .thread-group {
+        display: block;
+        max-width: var(--content-width, 80ch);
+        white-space: normal;
+      }
       .diffContainer {
         display: flex;
         font-family: var(--monospace-font-family);
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.js b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.js
index 557a652..76a62b8 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.js
@@ -365,7 +365,7 @@
     },
 
     _getThreadGroupForLine(contentEl) {
-      return contentEl.querySelector('gr-diff-comment-thread-group');
+      return contentEl.querySelector('.thread-group');
     },
 
     /**
@@ -378,7 +378,8 @@
       // Check if thread group exists.
       let threadGroupEl = this._getThreadGroupForLine(contentEl);
       if (!threadGroupEl) {
-        threadGroupEl = document.createElement('gr-diff-comment-thread-group');
+        threadGroupEl = document.createElement('div');
+        threadGroupEl.className = 'thread-group';
         contentEl.appendChild(threadGroupEl);
       }
       return threadGroupEl;
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff_test.html b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff_test.html
index 316990d..4befd2f 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff_test.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff_test.html
@@ -315,8 +315,7 @@
         // The new thread group can be fetched.
         assert.isOk(element._getThreadGroupForLine(contentEl));
 
-        assert.equal(contentEl.querySelectorAll(
-            'gr-diff-comment-thread-group').length, 1);
+        assert.equal(contentEl.querySelectorAll('.thread-group').length, 1);
       });
 
       suite('image diffs', () => {