diff --git a/src/blockchain_db/lmdb/db_lmdb.cpp b/src/blockchain_db/lmdb/db_lmdb.cpp
index 340434888..3278c7387 100644
--- a/src/blockchain_db/lmdb/db_lmdb.cpp
+++ b/src/blockchain_db/lmdb/db_lmdb.cpp
@@ -707,7 +707,7 @@ uint64_t BlockchainLMDB::get_estimated_batch_size(uint64_t batch_num_blocks, uin
       ++num_blocks_used;
     }
     if (my_rtxn) block_rtxn_stop();
-    avg_block_size = total_block_size / num_blocks_used;
+    avg_block_size = total_block_size / (num_blocks_used ? num_blocks_used : 1);
     MDEBUG("average block size across recent " << num_blocks_used << " blocks: " << avg_block_size);
   }
 estim:
diff --git a/src/blockchain_utilities/blockchain_blackball.cpp b/src/blockchain_utilities/blockchain_blackball.cpp
index 6ff184041..f824d93a6 100644
--- a/src/blockchain_utilities/blockchain_blackball.cpp
+++ b/src/blockchain_utilities/blockchain_blackball.cpp
@@ -637,6 +637,7 @@ static void inc_per_amount_outputs(MDB_txn *txn, uint64_t amount, uint64_t total
   v.mv_size = 2 * sizeof(uint64_t);
   v.mv_data = (void*)data;
   dbr = mdb_cursor_put(cur, &k, &v, 0);
+  CHECK_AND_ASSERT_THROW_MES(!dbr, "Failed to write record for per amount outputs: " + std::string(mdb_strerror(dbr)));
   mdb_cursor_close(cur);
 }
 
diff --git a/src/cryptonote_core/cryptonote_core.cpp b/src/cryptonote_core/cryptonote_core.cpp
index be1ea5a17..beafa5e3b 100644
--- a/src/cryptonote_core/cryptonote_core.cpp
+++ b/src/cryptonote_core/cryptonote_core.cpp
@@ -447,6 +447,7 @@ namespace cryptonote
       m_nettype = FAKECHAIN;
     }
     bool r = handle_command_line(vm);
+    CHECK_AND_ASSERT_MES(r, false, "Failed to handle command line");
 
     std::string db_type = command_line::get_arg(vm, cryptonote::arg_db_type);
     std::string db_sync_mode = command_line::get_arg(vm, cryptonote::arg_db_sync_mode);
@@ -634,6 +635,7 @@ namespace cryptonote
     };
     const difficulty_type fixed_difficulty = command_line::get_arg(vm, arg_fixed_difficulty);
     r = m_blockchain_storage.init(db.release(), m_nettype, m_offline, regtest ? &regtest_test_options : test_options, fixed_difficulty, get_checkpoints);
+    CHECK_AND_ASSERT_MES(r, false, "Failed to initialize blockchain storage");
 
     r = m_mempool.init(max_txpool_weight);
     CHECK_AND_ASSERT_MES(r, false, "Failed to initialize memory pool");
diff --git a/src/rpc/core_rpc_server.cpp b/src/rpc/core_rpc_server.cpp
index c41fb37d8..4c73a8bb3 100644
--- a/src/rpc/core_rpc_server.cpp
+++ b/src/rpc/core_rpc_server.cpp
@@ -1510,7 +1510,7 @@ namespace cryptonote
       ok = ok && getheight_res.status == CORE_RPC_STATUS_OK;
 
       m_should_use_bootstrap_daemon = ok && top_height + 10 < getheight_res.height;
-      MINFO((m_should_use_bootstrap_daemon ? "Using" : "Not using") << " the bootstrap daemon (our height: " << top_height << ", bootstrap daemon's height: " << getheight_res.height << ")");
+      MINFO((m_should_use_bootstrap_daemon ? "Using" : "Not using") << " the bootstrap daemon (our height: " << top_height << ", bootstrap daemon's height: " << (ok ? getheight_res.height : 0) << ")");
     }
     if (!m_should_use_bootstrap_daemon)
       return false;
diff --git a/tests/core_tests/chaingen.cpp b/tests/core_tests/chaingen.cpp
index 614585349..8dde1f475 100644
--- a/tests/core_tests/chaingen.cpp
+++ b/tests/core_tests/chaingen.cpp
@@ -546,6 +546,7 @@ void block_tracker::global_indices(const cryptonote::transaction *tx, std::vecto
 void block_tracker::get_fake_outs(size_t num_outs, uint64_t amount, uint64_t global_index, uint64_t cur_height, std::vector<get_outs_entry> &outs){
   auto & vct = m_outs[amount];
   const size_t n_outs = vct.size();
+  CHECK_AND_ASSERT_THROW_MES(n_outs > 0, "n_outs is 0");
 
   std::set<size_t> used;
   std::vector<size_t> choices;
diff --git a/tests/core_tests/wallet_tools.cpp b/tests/core_tests/wallet_tools.cpp
index d9cee34c1..21a9455c0 100644
--- a/tests/core_tests/wallet_tools.cpp
+++ b/tests/core_tests/wallet_tools.cpp
@@ -163,6 +163,7 @@ bool wallet_tools::fill_tx_sources(tools::wallet2 * wallet, std::vector<cryptono
 
 void wallet_tools::gen_tx_src(size_t mixin, uint64_t cur_height, const tools::wallet2::transfer_details & td, cryptonote::tx_source_entry & src, block_tracker &bt)
 {
+  CHECK_AND_ASSERT_THROW_MES(mixin != 0, "mixin is zero");
   src.amount = td.amount();
   src.rct = td.is_rct();
 
diff --git a/tests/unit_tests/test_protocol_pack.cpp b/tests/unit_tests/test_protocol_pack.cpp
index 7329c0d23..0ae2e9c68 100644
--- a/tests/unit_tests/test_protocol_pack.cpp
+++ b/tests/unit_tests/test_protocol_pack.cpp
@@ -48,6 +48,7 @@ TEST(protocol_pack, protocol_pack_command)
 
     cryptonote::NOTIFY_RESPONSE_CHAIN_ENTRY::request r2;
     res = epee::serialization::load_t_from_binary(r2, buff);
+    ASSERT_TRUE(res);
     ASSERT_TRUE(r.m_block_ids.size() == i);
     ASSERT_TRUE(r.start_height == 1);
     ASSERT_TRUE(r.total_height == 3);