diff --git a/Telegram/SourceFiles/data/data_forum.cpp b/Telegram/SourceFiles/data/data_forum.cpp
index 3890b4c0ed..0a20f0aeac 100644
--- a/Telegram/SourceFiles/data/data_forum.cpp
+++ b/Telegram/SourceFiles/data/data_forum.cpp
@@ -13,6 +13,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "data/data_session.h"
 #include "data/data_forum_icons.h"
 #include "data/data_forum_topic.h"
+#include "data/data_replies_list.h"
 #include "data/notify/data_notify_settings.h"
 #include "history/history.h"
 #include "history/history_item.h"
@@ -276,6 +277,33 @@ Thread *Forum::activeSubsectionThread() const {
 	return _activeSubsectionTopic;
 }
 
+void Forum::markUnreadCountsUnknown(MsgId readTillId) {
+	if (!channel()->useSubsectionTabs()) {
+		return;
+	}
+	for (const auto &[rootId, topic] : _topics) {
+		const auto replies = topic->replies();
+		if (replies->unreadCountCurrent() > 0) {
+			replies->setInboxReadTill(readTillId, std::nullopt);
+		}
+	}
+}
+
+void Forum::updateUnreadCounts(
+		MsgId readTillId,
+		const base::flat_map<not_null<ForumTopic*>, int> &counts) {
+	if (!channel()->useSubsectionTabs()) {
+		return;
+	}
+	for (const auto &[rootId, topic] : _topics) {
+		const auto raw = topic.get();
+		const auto replies = raw->replies();
+		const auto i = counts.find(raw);
+		const auto count = (i != end(counts)) ? i->second : 0;
+		replies->setInboxReadTill(readTillId, count);
+	}
+}
+
 void Forum::listMessageChanged(HistoryItem *from, HistoryItem *to) {
 	if (from || to) {
 		reorderLastTopics();
diff --git a/Telegram/SourceFiles/data/data_forum.h b/Telegram/SourceFiles/data/data_forum.h
index ae0cc2d1a5..cccacadeef 100644
--- a/Telegram/SourceFiles/data/data_forum.h
+++ b/Telegram/SourceFiles/data/data_forum.h
@@ -99,6 +99,11 @@ public:
 	void saveActiveSubsectionThread(not_null<Thread*> thread);
 	[[nodiscard]] Thread *activeSubsectionThread() const;
 
+	void markUnreadCountsUnknown(MsgId readTillId);
+	void updateUnreadCounts(
+		MsgId readTillId,
+		const base::flat_map<not_null<ForumTopic*>, int> &counts);
+
 	[[nodiscard]] rpl::lifetime &lifetime() {
 		return _lifetime;
 	}
diff --git a/Telegram/SourceFiles/data/data_histories.cpp b/Telegram/SourceFiles/data/data_histories.cpp
index f114f6d433..30983b9347 100644
--- a/Telegram/SourceFiles/data/data_histories.cpp
+++ b/Telegram/SourceFiles/data/data_histories.cpp
@@ -713,7 +713,7 @@ void Histories::sendReadRequest(not_null<History*> history, State &state) {
 			} else {
 				Assert(!state->sentReadTill || state->sentReadTill > tillId);
 			}
-			history->validateMonoforumUnread(tillId);
+			history->validateMonoAndForumUnread(tillId);
 			sendReadRequests();
 			finish();
 		};
diff --git a/Telegram/SourceFiles/history/history.cpp b/Telegram/SourceFiles/history/history.cpp
index ed146023f4..88a786f38a 100644
--- a/Telegram/SourceFiles/history/history.cpp
+++ b/Telegram/SourceFiles/history/history.cpp
@@ -33,6 +33,7 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "data/data_channel_admins.h"
 #include "data/data_changes.h"
 #include "data/data_chat_filters.h"
+#include "data/data_replies_list.h"
 #include "data/data_send_action.h"
 #include "data/data_star_gift.h"
 #include "data/data_emoji_statuses.h"
@@ -3156,6 +3157,58 @@ void History::applyDialogTopMessage(MsgId topMessageId) {
 	}
 }
 
+void History::tryMarkForumIntervalRead(
+		MsgId wasInboxReadBefore,
+		MsgId nowInboxReadBefore) {
+	if (!isForum()
+		|| !peer->asChannel()->useSubsectionTabs()
+		|| (nowInboxReadBefore <= wasInboxReadBefore)) {
+		return;
+	} else if (loadedAtBottom() && nowInboxReadBefore >= minMsgId()) {
+		// Count for each sublist how many messages are still not read.
+		auto counts = base::flat_map<not_null<Data::ForumTopic*>, int>();
+		for (const auto &block : blocks) {
+			for (const auto &message : block->messages) {
+				const auto item = message->data();
+				if (!item->isRegular() || item->id < nowInboxReadBefore) {
+					continue;
+				}
+				if (const auto topic = item->topic()) {
+					++counts[topic];
+				}
+			}
+		}
+		if (const auto forum = peer->forum()) {
+			forum->updateUnreadCounts(nowInboxReadBefore - 1, counts);
+		}
+	} else if (minMsgId() <= wasInboxReadBefore
+		&& maxMsgId() >= nowInboxReadBefore) {
+		// Count for each sublist how many messages were read.
+		for (const auto &block : blocks) {
+			for (const auto &message : block->messages) {
+				const auto item = message->data();
+				if (!item->isRegular() || item->id < wasInboxReadBefore) {
+					continue;
+				} else if (item->id >= nowInboxReadBefore) {
+					break;
+				}
+				if (const auto topic = item->topic()) {
+					const auto replies = topic->replies();
+					const auto unread = replies->unreadCountCurrent();
+					if (unread > 0) {
+						replies->setInboxReadTill(item->id, unread - 1);
+					}
+				}
+			}
+		}
+	} else {
+		// We can't invalidate sublist unread counts here, because no read
+		// request was yet sent to the server (so it can't return correct
+		// values yet), we need to do that after we send read request.
+		_flags |= Flag::MonoAndForumUnreadInvalidatePending;
+	}
+}
+
 void History::tryMarkMonoforumIntervalRead(
 		MsgId wasInboxReadBefore,
 		MsgId nowInboxReadBefore) {
@@ -3201,24 +3254,29 @@ void History::tryMarkMonoforumIntervalRead(
 		// We can't invalidate sublist unread counts here, because no read
 		// request was yet sent to the server (so it can't return correct
 		// values yet), we need to do that after we send read request.
-		_flags |= Flag::MonoforumUnreadInvalidatePending;
+		_flags |= Flag::MonoAndForumUnreadInvalidatePending;
 	}
 }
 
-void History::validateMonoforumUnread(MsgId readTillId) {
-	if (!(_flags & Flag::MonoforumUnreadInvalidatePending)) {
+void History::validateMonoAndForumUnread(MsgId readTillId) {
+	if (!(_flags & Flag::MonoAndForumUnreadInvalidatePending)) {
 		return;
 	}
-	_flags &= ~Flag::MonoforumUnreadInvalidatePending;
-	if (!amMonoforumAdmin()) {
-		return;
-	} else if (const auto monoforum = peer->monoforum()) {
-		monoforum->markUnreadCountsUnknown(readTillId);
+	_flags &= ~Flag::MonoAndForumUnreadInvalidatePending;
+	if (isForum()) {
+		if (const auto forum = peer->forum()) {
+			forum->markUnreadCountsUnknown(readTillId);
+		}
+	} else if (amMonoforumAdmin()) {
+		if (const auto monoforum = peer->monoforum()) {
+			monoforum->markUnreadCountsUnknown(readTillId);
+		}
 	}
 }
 
 void History::setInboxReadTill(MsgId upTo) {
 	if (_inboxReadBefore) {
+		tryMarkForumIntervalRead(*_inboxReadBefore, upTo + 1);
 		tryMarkMonoforumIntervalRead(*_inboxReadBefore, upTo + 1);
 		accumulate_max(*_inboxReadBefore, upTo + 1);
 	} else {
diff --git a/Telegram/SourceFiles/history/history.h b/Telegram/SourceFiles/history/history.h
index 047a341094..40ee83ceef 100644
--- a/Telegram/SourceFiles/history/history.h
+++ b/Telegram/SourceFiles/history/history.h
@@ -434,7 +434,10 @@ public:
 	void tryMarkMonoforumIntervalRead(
 		MsgId wasInboxReadBefore,
 		MsgId nowInboxReadBefore);
-	void validateMonoforumUnread(MsgId readTillId);
+	void tryMarkForumIntervalRead(
+		MsgId wasInboxReadBefore,
+		MsgId nowInboxReadBefore);
+	void validateMonoAndForumUnread(MsgId readTillId);
 
 	[[nodiscard]] bool isTopPromoted() const;
 
@@ -480,7 +483,7 @@ private:
 		FakeUnreadWhileOpened = (1 << 5),
 		HasPinnedMessages = (1 << 6),
 		ResolveChatListMessage = (1 << 7),
-		MonoforumUnreadInvalidatePending = (1 << 8),
+		MonoAndForumUnreadInvalidatePending = (1 << 8),
 	};
 	using Flags = base::flags<Flag>;
 	friend inline constexpr auto is_flag_type(Flag) {