diff --git a/webextensions/common/Tab.js b/webextensions/common/Tab.js
index 3b51d6ed3..4c03d8bc8 100644
--- a/webextensions/common/Tab.js
+++ b/webextensions/common/Tab.js
@@ -1131,12 +1131,6 @@ export default class Tab {
       this.states.add(state);
 
     switch (state) {
-      case Constants.kTAB_STATE_ACTIVE:
-        if (this.element &&
-            this.element.parentNode)
-          this.element.parentNode.setAttribute('aria-activedescendant', this.element.id);
-        break;
-
       case Constants.kTAB_STATE_HIGHLIGHTED:
         if (this.element)
           this.element.setAttribute('aria-selected', 'true');
diff --git a/webextensions/sidebar/sidebar-tabs.js b/webextensions/sidebar/sidebar-tabs.js
index d7d4bbc30..5921ac61b 100644
--- a/webextensions/sidebar/sidebar-tabs.js
+++ b/webextensions/sidebar/sidebar-tabs.js
@@ -611,8 +611,13 @@ BackgroundConnection.onMessage.addListener(async message => {
       const tab = Tab.get(lastMessage.tabId);
       if (!tab)
         return;
+      const lastActive = TabsStore.activeTabInWindow.get(lastMessage.windowId);
+      if (lastActive &&
+          lastActive.$TST.element)
+        lastActive.$TST.element.parentNode.removeAttribute('aria-activedescendant');
       TabsStore.activeTabInWindow.set(lastMessage.windowId, tab);
       TabsInternalOperation.setTabActive(tab);
+      tab.$TST.element.parentNode.setAttribute('aria-activedescendant', tab.$TST.element.id);
     }; break;
 
     case Constants.kCOMMAND_NOTIFY_TAB_UPDATED: {