diff --git a/src/contentScripts/communityConsole/batchLock.js b/src/contentScripts/communityConsole/batchLock.js
index 86a7057..db08a06 100644
--- a/src/contentScripts/communityConsole/batchLock.js
+++ b/src/contentScripts/communityConsole/batchLock.js
@@ -1,19 +1,12 @@
 import {isOptionEnabled} from '../../common/optionsUtils.js';
 
-import {addButtonToThreadListActions, removeChildNodes} from './utils/common.js';
+import {addButtonToThreadListActions, removeChildNodes, shouldAddBtnToActionBar} from './utils/common.js';
+
+const kLockDebugId = 'twpt-lock';
 
 export var batchLock = {
-  nodeIsReadToggleBtn(node) {
-    return ('tagName' in node) && node.tagName == 'MATERIAL-BUTTON' &&
-        node.getAttribute('debugid') !== null &&
-        (node.getAttribute('debugid') == 'mark-read-button' ||
-         node.getAttribute('debugid') == 'mark-unread-button') &&
-        ('parentNode' in node) && node.parentNode !== null &&
-        ('parentNode' in node.parentNode) &&
-        node.parentNode.querySelector('[debugid="twpt-lock"]') === null &&
-        node.parentNode.parentNode !== null &&
-        ('tagName' in node.parentNode.parentNode) &&
-        node.parentNode.parentNode.tagName == 'EC-BULK-ACTIONS';
+  shouldAddButton(node) {
+    return shouldAddBtnToActionBar(kLockDebugId, node);
   },
   createDialog() {
     var modal = document.querySelector('.pane[pane-id="default-1"]');
@@ -119,7 +112,7 @@
       if (isEnabled) {
         let tooltip = chrome.i18n.getMessage('inject_lockbtn');
         let btn = addButtonToThreadListActions(
-            readToggle, 'lock', 'twpt-lock', tooltip);
+            readToggle, 'lock', kLockDebugId, tooltip);
         btn.addEventListener('click', () => {
           this.createDialog();
         });
diff --git a/src/contentScripts/communityConsole/main.js b/src/contentScripts/communityConsole/main.js
index 34b0f1d..95045a4 100644
--- a/src/contentScripts/communityConsole/main.js
+++ b/src/contentScripts/communityConsole/main.js
@@ -130,7 +130,7 @@
 
     // Inject the batch lock button in the thread list if the option is
     // currently enabled.
-    if (batchLock.nodeIsReadToggleBtn(node)) {
+    if (batchLock.shouldAddButton(node)) {
       batchLock.addButtonIfEnabled(node);
     }
 
diff --git a/src/contentScripts/communityConsole/utils/common.js b/src/contentScripts/communityConsole/utils/common.js
index ac4db4e..2e33f99 100644
--- a/src/contentScripts/communityConsole/utils/common.js
+++ b/src/contentScripts/communityConsole/utils/common.js
@@ -61,6 +61,17 @@
   return clone;
 }
 
+// Returns true if |node| is the "mark as read/unread" button, the parent of the
+// parent of |node| is the actions bar of the thread list, and the button with
+// debugid |debugid| is NOT part of the actions bar.
+export function shouldAddBtnToActionBar(debugid, node) {
+  return node?.tagName == 'MATERIAL-BUTTON' &&
+      (node.getAttribute?.('debugid') == 'mark-read-button' ||
+       node.getAttribute?.('debugid') == 'mark-unread-button') &&
+      node.parentNode?.querySelector('[debugid="' + debugid + '"]') === null &&
+      node.parentNode?.parentNode?.tagName == 'EC-BULK-ACTIONS';
+}
+
 // Returns the display language set by the user.
 export function getDisplayLanguage() {
   var startup =