diff --git a/src/api/gramjs/methods/messages.ts b/src/api/gramjs/methods/messages.ts
index d4a1cae9c..c237193cf 100644
--- a/src/api/gramjs/methods/messages.ts
+++ b/src/api/gramjs/methods/messages.ts
@@ -958,6 +958,12 @@ export async function markMessageListRead({
 
   if (threadId === MAIN_THREAD_ID) {
     void requestChatUpdate({ chat, noLastMessage: true });
+  } else if (chat.isForum) {
+    onUpdate({
+      '@type': 'updateTopic',
+      chatId: chat.id,
+      topicId: Number(threadId),
+    });
   }
 }
 
diff --git a/src/global/actions/api/messages.ts b/src/global/actions/api/messages.ts
index 031eca38e..e14777220 100644
--- a/src/global/actions/api/messages.ts
+++ b/src/global/actions/api/messages.ts
@@ -857,7 +857,7 @@ addActionHandler('markMessageListRead', (global, actions, payload): ActionReturn
     return global;
   }
 
-  const readCount = countSortedIds(viewportIds!, minId, maxId);
+  const readCount = countSortedIds(viewportIds, minId, maxId);
   if (!readCount) {
     return global;
   }
@@ -2136,6 +2136,9 @@ addActionHandler('copyMessageLink', async (global, actions, payload): Promise<vo
 });
 
 function countSortedIds(ids: number[], from: number, to: number) {
+  // If ids are outside viewport, we cannot get correct count
+  if (ids.length === 0 || from < ids[0] || to > ids[ids.length - 1]) return undefined;
+
   let count = 0;
 
   for (let i = 0, l = ids.length; i < l; i++) {