diff --git a/crypto/block/mc-config.cpp b/crypto/block/mc-config.cpp
index 0f019b068..554a70d9e 100644
--- a/crypto/block/mc-config.cpp
+++ b/crypto/block/mc-config.cpp
@@ -516,34 +516,50 @@ td::Result<std::unique_ptr<ValidatorSet>> Config::unpack_validator_set(Ref<vm::C
         "maximal index in a validator set dictionary must be one less than the total number of validators");
   }
   auto ptr = std::make_unique<ValidatorSet>(rec.utime_since, rec.utime_until, rec.total, rec.main);
-  for (int i = 0; i < rec.total; i++) {
-    key_buffer.store_ulong(i);
-    auto descr_cs = dict.lookup(key_buffer.bits(), 16);
-    if (descr_cs.is_null()) {
-      return td::Status::Error("indices in a validator set dictionary must be integers 0..total-1");
-    }
+
+  std::vector<bool> seen_keys(rec.total);
+  td::Status error;
+
+  auto validator_set_check_fn = [&](Ref<vm::CellSlice> descr_cs, td::ConstBitPtr key, int n) -> bool {
+    int i = static_cast<int>(key.get_int(n));
+    CHECK(i >= 0 && i < rec.total && !seen_keys[i]);
+    seen_keys[i] = true;
+
     gen::ValidatorDescr::Record_validator_addr descr;
     if (!tlb::csr_unpack(descr_cs, descr)) {
       descr.adnl_addr.set_zero();
       if (!(gen::t_ValidatorDescr.unpack_validator(descr_cs.write(), descr.public_key, descr.weight) &&
             descr_cs->empty_ext())) {
-        return td::Status::Error(PSLICE() << "validator #" << i
-                                          << " has an invalid ValidatorDescr record in the validator set dictionary");
+        error = td::Status::Error(PSLICE() << "validator #" << i
+                                           << " has an invalid ValidatorDescr record in the validator set dictionary");
+        return false;
       }
     }
     gen::SigPubKey::Record sig_pubkey;
     if (!tlb::csr_unpack(std::move(descr.public_key), sig_pubkey)) {
-      return td::Status::Error(PSLICE() << "validator #" << i
-                                        << " has no public key or its public key is in unsupported format");
+      error = td::Status::Error(PSLICE() << "validator #" << i
+                                         << " has no public key or its public key is in unsupported format");
+      return false;
     }
     if (!descr.weight) {
-      return td::Status::Error(PSLICE() << "validator #" << i << " has zero weight");
+      error = td::Status::Error(PSLICE() << "validator #" << i << " has zero weight");
+      return false;
     }
     if (descr.weight > ~(ptr->total_weight)) {
-      return td::Status::Error("total weight of all validators in validator set exceeds 2^64");
+      error = td::Status::Error("total weight of all validators in validator set exceeds 2^64");
+      return false;
     }
     ptr->list.emplace_back(sig_pubkey.pubkey, descr.weight, ptr->total_weight, descr.adnl_addr);
     ptr->total_weight += descr.weight;
+    return true;
+  };
+
+  if (!dict.check_for_each(validator_set_check_fn)) {
+    CHECK(error.is_error());
+    return error;
+  }
+  if (std::find(seen_keys.begin(), seen_keys.end(), false) != seen_keys.end()) {
+    return td::Status::Error("indices in a validator set dictionary must be integers 0..total-1");
   }
   if (rec.total_weight && rec.total_weight != ptr->total_weight) {
     return td::Status::Error("validator set declares incorrect total weight");