diff --git a/validator/full-node-shard.cpp b/validator/full-node-shard.cpp
index e491061e..d048f611 100644
--- a/validator/full-node-shard.cpp
+++ b/validator/full-node-shard.cpp
@@ -670,7 +670,7 @@ void FullNodeShardImpl::process_broadcast(PublicKeyHash src, ton_api::tonNode_ne
 
 void FullNodeShardImpl::process_broadcast(PublicKeyHash src, ton_api::tonNode_blockBroadcast &query) {
   BlockIdExt block_id = create_block_id(query.id_);
-  //if (block_id.shard_full() != shard_) {
+  //if (!shard_is_ancestor(shard_, block_id.shard_full())) {
   //  LOG(FULL_NODE_WARNING) << "dropping block broadcast: shard mismatch. overlay=" << shard_.to_str()
   //                         << " block=" << block_id.to_str();
   //  return;
diff --git a/validator/full-node.cpp b/validator/full-node.cpp
index 52d3cfb9..72af6fe8 100644
--- a/validator/full-node.cpp
+++ b/validator/full-node.cpp
@@ -135,10 +135,18 @@ void FullNodeImpl::initial_read_complete(BlockHandle top_handle) {
 void FullNodeImpl::update_shard_configuration(td::Ref<MasterchainState> state, std::set<ShardIdFull> shards_to_monitor,
                                               std::set<ShardIdFull> temporary_shards) {
   CHECK(shards_to_monitor.count(ShardIdFull(masterchainId)));
-  std::map<ShardIdFull, BlockIdExt> new_shards;
+  std::set<ShardIdFull> new_shards;
   std::map<ShardIdFull, FullNodeShardMode> new_active;
-  new_shards[ShardIdFull(masterchainId)] = state->get_block_id();
+  new_shards.insert(ShardIdFull(masterchainId));
   std::set<WorkchainId> workchains;
+  auto cut_shard = [&](ShardIdFull shard) -> ShardIdFull {
+    unsigned pfx_len = shard.pfx_len();
+    unsigned min_split = state->soft_min_split_depth(shard.workchain);
+    if (min_split < pfx_len) {
+      return shard_prefix(shard, min_split);
+    }
+    return shard;
+  };
   auto set_active = [&](ShardIdFull shard, FullNodeShardMode mode) {
     while (new_active.emplace(shard, mode).second && shard.pfx_len() > 0) {
       shard = shard_parent(shard);
@@ -146,20 +154,20 @@ void FullNodeImpl::update_shard_configuration(td::Ref<MasterchainState> state, s
   };
   for (auto &info : state->get_shards()) {
     workchains.insert(info->shard().workchain);
-    new_shards[info->shard()] = info->top_block_id();
+    new_shards.insert(cut_shard(info->shard()));
   }
   for (const auto &wpair : state->get_workchain_list()) {
     ton::WorkchainId wc = wpair.first;
     const block::WorkchainInfo *winfo = wpair.second.get();
     if (workchains.count(wc) == 0 && winfo->active && winfo->enabled_since <= state->get_unix_time()) {
-      new_shards[ShardIdFull(wc)] = BlockIdExt(wc, shardIdAll, 0, winfo->zerostate_root_hash, winfo->zerostate_file_hash);
+      new_shards.insert(ShardIdFull(wc));
     }
   }
   for (ShardIdFull shard : shards_to_monitor) {
-    set_active(shard, FullNodeShardMode::active);
+    set_active(cut_shard(shard), FullNodeShardMode::active);
   }
   for (ShardIdFull shard : temporary_shards) {
-    set_active(shard, FullNodeShardMode::active_temp);
+    set_active(cut_shard(shard), FullNodeShardMode::active_temp);
   }
 
   auto info_set_mode = [&](ShardIdFull shard, ShardInfo& info, FullNodeShardMode mode) {
@@ -177,7 +185,7 @@ void FullNodeImpl::update_shard_configuration(td::Ref<MasterchainState> state, s
   };
 
   for (auto shard : new_shards) {
-    auto &info = shards_[shard.first];
+    auto &info = shards_[shard];
     info.exists = true;
   }
 
@@ -283,7 +291,7 @@ void FullNodeImpl::send_shard_block_info(BlockIdExt block_id, CatchainSeqno cc_s
 }
 
 void FullNodeImpl::send_broadcast(BlockBroadcast broadcast) {
-  auto shard = get_shard(broadcast.block_id.shard_full(), true);
+  auto shard = get_shard(broadcast.block_id.shard_full());
   if (shard.empty()) {
     VLOG(FULL_NODE_WARNING) << "dropping OUT broadcast to unknown shard";
     return;
@@ -379,27 +387,28 @@ void FullNodeImpl::download_out_msg_queue_proof(BlockIdExt block_id, ShardIdFull
                           std::move(promise));
 }
 
-td::actor::ActorId<FullNodeShard> FullNodeImpl::get_shard(ShardIdFull shard, bool exact) {
-  if (!exact) {
-    ShardIdFull s = shard;
-    while (true) {
-      auto it = shards_.find(s);
-      if (it != shards_.end() && it->second.exists) {
-        if (it->second.actor.empty()) {
-          add_shard_actor(s, FullNodeShardMode::inactive);
-        }
-        if (it->second.mode == FullNodeShardMode::inactive) {
-          it->second.delete_at = td::Timestamp::in(INACTIVE_SHARD_TTL);
-        }
-        return it->second.actor.get();
+td::actor::ActorId<FullNodeShard> FullNodeImpl::get_shard(ShardIdFull shard) {
+  while (true) {
+    auto it = shards_.find(shard);
+    if (it != shards_.end() && it->second.exists) {
+      if (it->second.actor.empty()) {
+        add_shard_actor(shard, FullNodeShardMode::inactive);
       }
-      if (s.pfx_len() == 0) {
-        break;
+      if (it->second.mode == FullNodeShardMode::inactive) {
+        it->second.delete_at = td::Timestamp::in(INACTIVE_SHARD_TTL);
       }
-      s = shard_parent(s);
+      return it->second.actor.get();
     }
+    if (shard.pfx_len() == 0) {
+      break;
+    }
+    shard = shard_parent(shard);
   }
-  auto &info = shards_[shard];
+  auto it = shards_.find(shard);
+  if (it == shards_.end()) {
+    it = shards_.emplace(shard = ShardIdFull(shard.workchain), ShardInfo{}).first;
+  }
+  auto &info = it->second;
   if (info.actor.empty()) {
     add_shard_actor(shard, FullNodeShardMode::inactive);
   }
diff --git a/validator/full-node.hpp b/validator/full-node.hpp
index 8cc8994b..503ba286 100644
--- a/validator/full-node.hpp
+++ b/validator/full-node.hpp
@@ -108,7 +108,7 @@ class FullNodeImpl : public FullNode {
   FileHash zero_state_file_hash_;
 
   td::actor::ActorId<FullNodeShard> get_shard(AccountIdPrefixFull dst);
-  td::actor::ActorId<FullNodeShard> get_shard(ShardIdFull shard, bool exact = false);
+  td::actor::ActorId<FullNodeShard> get_shard(ShardIdFull shard);
   std::map<ShardIdFull, ShardInfo> shards_;
 
   td::actor::ActorId<keyring::Keyring> keyring_;
diff --git a/validator/manager-init.cpp b/validator/manager-init.cpp
index 1a322c02..8935664e 100644
--- a/validator/manager-init.cpp
+++ b/validator/manager-init.cpp
@@ -566,7 +566,7 @@ void ValidatorManagerMasterchainStarter::truncated() {
   truncate_shard_next(handle_->id(), ig.get_promise());
   auto s = state_->get_shards();
   for (auto &shard : s) {
-    if (opts_->need_monitor(shard->shard())) {
+    if (opts_->need_monitor(shard->shard(), state_)) {
       truncate_shard_next(shard->top_block_id(), ig.get_promise());
     }
   }
diff --git a/validator/manager.cpp b/validator/manager.cpp
index 95ef6bf0..2a17af5e 100644
--- a/validator/manager.cpp
+++ b/validator/manager.cpp
@@ -214,7 +214,7 @@ void ValidatorManagerImpl::prevalidate_block(BlockBroadcast broadcast, td::Promi
     promise.set_error(td::Status::Error(ErrorCode::notready, "node not started"));
     return;
   }
-  if (!shards_to_monitor_.count(broadcast.block_id.shard_full())) {
+  if (!need_monitor(broadcast.block_id.shard_full())) {
     promise.set_error(td::Status::Error("not monitoring shard"));
     return;
   }
@@ -457,7 +457,7 @@ void ValidatorManagerImpl::add_shard_block_description(td::Ref<ShardTopBlockDesc
     }
     shard_blocks_[ShardTopBlockDescriptionId{desc->block_id().shard_full(), desc->catchain_seqno()}] = desc;
     VLOG(VALIDATOR_DEBUG) << "new shard block descr for " << desc->block_id();
-    if (shards_to_monitor_.count(desc->block_id().shard_full())) {
+    if (need_monitor(desc->block_id().shard_full())) {
       auto P = td::PromiseCreator::lambda([](td::Result<td::Ref<ShardState>> R) {
         if (R.is_error()) {
           auto S = R.move_as_error();
@@ -617,10 +617,9 @@ void ValidatorManagerImpl::wait_out_msg_queue_proof(BlockIdExt block_id, ShardId
           td::actor::send_closure(SelfId, &ValidatorManagerImpl::finished_wait_msg_queue, block_id, dst_shard,
                                   std::move(R));
         });
-    auto id = td::actor::create_actor<WaitOutMsgQueueProof>("waitmsgqueue", block_id, dst_shard,
-                                                            shards_to_monitor_.count(block_id.shard_full()), priority,
-                                                            actor_id(this), td::Timestamp::at(timeout.at() + 10.0),
-                                                            std::move(P))
+    auto id = td::actor::create_actor<WaitOutMsgQueueProof>(
+                  "waitmsgqueue", block_id, dst_shard, need_monitor(block_id.shard_full()), priority, actor_id(this),
+                  td::Timestamp::at(timeout.at() + 10.0), std::move(P))
                   .release();
     wait_out_msg_queue_proof_[key].actor_ = id;
     it = wait_out_msg_queue_proof_.find(key);
@@ -1083,8 +1082,8 @@ void ValidatorManagerImpl::finished_wait_msg_queue(BlockIdExt block_id, ShardIdF
                                       std::move(R));
             });
         auto id = td::actor::create_actor<WaitOutMsgQueueProof>("waitmsgqueue", block_id, dst_shard,
-                                                                shards_to_monitor_.count(block_id.shard_full()),
-                                                                X.second, actor_id(this), X.first, std::move(P))
+                                                                need_monitor(block_id.shard_full()), X.second,
+                                                                actor_id(this), X.first, std::move(P))
                       .release();
         it->second.actor_ = id;
         return;
@@ -2489,7 +2488,6 @@ void ValidatorManagerImpl::get_shard_client_state(bool from_db, td::Promise<Bloc
 
 void ValidatorManagerImpl::update_shard_configuration(td::Ref<MasterchainState> state,
                                                       std::set<ShardIdFull> shards_to_monitor) {
-  shards_to_monitor_ = shards_to_monitor;
   callback_->update_shard_configuration(std::move(state), std::move(shards_to_monitor), extra_active_shards_);
 }
 
diff --git a/validator/manager.hpp b/validator/manager.hpp
index ddef3441..3b32cfcd 100644
--- a/validator/manager.hpp
+++ b/validator/manager.hpp
@@ -628,11 +628,14 @@ class ValidatorManagerImpl : public ValidatorManager {
   td::Ref<PersistentStateDescription> get_block_persistent_state(BlockIdExt block_id);
 
  private:
+  bool need_monitor(ShardIdFull shard) const {
+    return opts_->need_monitor(shard, last_masterchain_state_);
+  }
+
   std::map<BlockSeqno, WaitList<td::actor::Actor, td::Unit>> shard_client_waiters_;
 
   std::map<adnl::AdnlNodeIdShort, td::actor::ActorOwn<CollatorNode>> collator_nodes_;
 
-  std::set<ShardIdFull> shards_to_monitor_ = {ShardIdFull(masterchainId)};
   std::set<ShardIdFull> extra_active_shards_;
   std::map<ShardIdFull, BlockSeqno> last_validated_blocks_;
 
diff --git a/validator/shard-client.cpp b/validator/shard-client.cpp
index 431d7721..5c25b783 100644
--- a/validator/shard-client.cpp
+++ b/validator/shard-client.cpp
@@ -91,7 +91,7 @@ void ShardClient::start_up_init_mode() {
 
   auto vec = masterchain_state_->get_shards();
   for (auto &shard : vec) {
-    if (shards_to_monitor_.count(shard->shard())) {
+    if (opts_->need_monitor(shard->shard(), masterchain_state_)) {
       auto P = td::PromiseCreator::lambda([promise = ig.get_promise()](td::Result<td::Ref<ShardState>> R) mutable {
         R.ensure();
         promise.set_value(td::Unit());
@@ -192,7 +192,7 @@ void ShardClient::apply_all_shards() {
 
   auto vec = masterchain_state_->get_shards();
   for (auto &shard : vec) {
-    if (shards_to_monitor_.count(shard->shard())) {
+    if (opts_->need_monitor(shard->shard(), masterchain_state_)) {
       auto Q = td::PromiseCreator::lambda([SelfId = actor_id(this), promise = ig.get_promise(),
                                            shard = shard->shard()](td::Result<td::Ref<ShardState>> R) mutable {
         if (R.is_error()) {
@@ -254,23 +254,9 @@ void ShardClient::build_shard_overlays() {
   for (const auto &info : masterchain_state_->get_shards()) {
     auto shard = info->shard();
     workchains.insert(shard.workchain);
-    bool will_split = shard.pfx_len() < max_shard_pfx_len &&
-                      (info->fsm_state() == McShardHash::FsmState::fsm_split || info->before_split());
-    bool will_merge =
-        shard.pfx_len() > 0 && (info->fsm_state() == McShardHash::FsmState::fsm_merge || info->before_merge());
-    if (opts_->need_monitor(shard) || (will_merge && opts_->need_monitor(shard_parent(shard)))) {
+    if (opts_->need_monitor(shard, masterchain_state_)) {
       new_shards_to_monitor.insert(shard);
     }
-    if (will_merge && opts_->need_monitor(shard_parent(shard))) {
-      new_shards_to_monitor.insert(shard_parent(shard));
-    }
-    if (will_split) {
-      for (int id = 0; id < 2; ++id) {
-        if (opts_->need_monitor(shard_child(shard, id))) {
-          new_shards_to_monitor.insert(shard_child(shard, id));
-        }
-      }
-    }
   }
 
   std::vector<BlockIdExt> new_workchains;
@@ -278,7 +264,8 @@ void ShardClient::build_shard_overlays() {
     ton::WorkchainId wc = wpair.first;
     const block::WorkchainInfo *winfo = wpair.second.get();
     auto shard = ShardIdFull(wc);
-    if (workchains.count(wc) == 0 && winfo->active && winfo->enabled_since <= cur_time && opts_->need_monitor(shard)) {
+    if (workchains.count(wc) == 0 && winfo->active && winfo->enabled_since <= cur_time &&
+        opts_->need_monitor(shard, masterchain_state_)) {
       new_shards_to_monitor.insert(shard);
       if (shards_to_monitor_.count(shard) == 0) {
         new_workchains.push_back(BlockIdExt(wc, shardIdAll, 0, winfo->zerostate_root_hash, winfo->zerostate_file_hash));
diff --git a/validator/state-serializer.cpp b/validator/state-serializer.cpp
index fc8cd29a..1c8d677c 100644
--- a/validator/state-serializer.cpp
+++ b/validator/state-serializer.cpp
@@ -159,16 +159,12 @@ void AsyncStateSerializer::next_iteration() {
       return;
     }
     while (next_idx_ < shards_.size()) {
-      if (!need_monitor(shards_[next_idx_].shard_full())) {
-        next_idx_++;
-      } else {
-          // block next attempts immediately, but send actual request later
-          running_ = true;
-          delay_action(
-            [SelfId = actor_id(this), shard = shards_[next_idx_]]() { td::actor::send_closure(SelfId, &AsyncStateSerializer::request_shard_state, shard); },
-            td::Timestamp::in(td::Random::fast(0, 4 * 3600)));
-        return;
-      }
+        // block next attempts immediately, but send actual request later
+        running_ = true;
+        delay_action(
+          [SelfId = actor_id(this), shard = shards_[next_idx_]]() { td::actor::send_closure(SelfId, &AsyncStateSerializer::request_shard_state, shard); },
+          td::Timestamp::in(td::Random::fast(0, 4 * 3600)));
+      return;
     }
     LOG(INFO) << "finished serializing persistent state for " << masterchain_handle_->id().id;
     last_key_block_ts_ = masterchain_handle_->unix_time();
@@ -245,7 +241,9 @@ void AsyncStateSerializer::got_masterchain_state(td::Ref<MasterchainState> state
 
   auto vec = state->get_shards();
   for (auto &v : vec) {
-    shards_.push_back(v->top_block_id());
+    if (opts_->need_monitor(v->shard(), state)) {
+      shards_.push_back(v->top_block_id());
+    }
   }
 
   auto write_data = [hash = state->root_cell()->get_hash(), cell_db_reader = cell_db_reader_] (td::FileFd& fd) {
@@ -311,10 +309,6 @@ void AsyncStateSerializer::success_handler() {
   next_iteration();
 }
 
-bool AsyncStateSerializer::need_monitor(ShardIdFull shard) {
-  return opts_->need_monitor(shard);
-}
-
 bool AsyncStateSerializer::need_serialize(BlockHandle handle) {
   if (handle->id().id.seqno == 0 || !handle->is_key_block()) {
     return false;
diff --git a/validator/state-serializer.hpp b/validator/state-serializer.hpp
index 0d6e9550..1472c3b4 100644
--- a/validator/state-serializer.hpp
+++ b/validator/state-serializer.hpp
@@ -60,7 +60,6 @@ class AsyncStateSerializer : public td::actor::Actor {
   }
 
   bool need_serialize(BlockHandle handle);
-  bool need_monitor(ShardIdFull shard);
 
   void alarm() override;
   void start_up() override;
diff --git a/validator/validator-options.hpp b/validator/validator-options.hpp
index b4a94a39..e96292ad 100644
--- a/validator/validator-options.hpp
+++ b/validator/validator-options.hpp
@@ -32,8 +32,9 @@ struct ValidatorManagerOptionsImpl : public ValidatorManagerOptions {
   BlockIdExt init_block_id() const override {
     return init_block_id_;
   }
-  bool need_monitor(ShardIdFull shard) const override {
-    return check_shard_(shard);
+  bool need_monitor(ShardIdFull shard, const td::Ref<MasterchainState>& state) const override {
+    td::uint32 min_split = state->min_split_depth(shard.workchain);
+    return check_shard_((td::uint32)shard.pfx_len() <= min_split ? shard : shard_prefix(shard, min_split));
   }
   bool allow_blockchain_init() const override {
     return allow_blockchain_init_;
diff --git a/validator/validator.h b/validator/validator.h
index 0daccc1a..c52cbad7 100644
--- a/validator/validator.h
+++ b/validator/validator.h
@@ -49,7 +49,7 @@ struct ValidatorManagerOptions : public td::CntObject {
  public:
   virtual BlockIdExt zero_block_id() const = 0;
   virtual BlockIdExt init_block_id() const = 0;
-  virtual bool need_monitor(ShardIdFull shard) const = 0;
+  virtual bool need_monitor(ShardIdFull shard, const td::Ref<MasterchainState>& state) const = 0;
   virtual bool allow_blockchain_init() const = 0;
   virtual double sync_blocks_before() const = 0;
   virtual double block_ttl() const = 0;