diff --git a/contrib/epee/include/net/abstract_tcp_server.h b/contrib/epee/include/net/abstract_tcp_server.h
index 000305cfa..cbad1717c 100644
--- a/contrib/epee/include/net/abstract_tcp_server.h
+++ b/contrib/epee/include/net/abstract_tcp_server.h
@@ -305,7 +305,7 @@ namespace net_utils
 		m_connections.back().powner = this;
 		m_connections.back().m_self_it = --m_connections.end();
 		m_connections.back().m_context.m_remote_address = remote_address;
-		m_connections.back().m_htread = threads_helper::create_thread(ConnectionHandlerProc, &m_connections.back());
+		m_connections.back().m_htread = threads_helper::create_thread(ConnectionHandlerProc, &m_connections.back()); // ugh, seems very risky
 
 		return true;
 	}
diff --git a/src/cryptonote_protocol/block_queue.cpp b/src/cryptonote_protocol/block_queue.cpp
index bfff35456..9e38ffbcb 100644
--- a/src/cryptonote_protocol/block_queue.cpp
+++ b/src/cryptonote_protocol/block_queue.cpp
@@ -62,6 +62,7 @@ void block_queue::add_blocks(uint64_t height, std::list<cryptonote::block_comple
 
 void block_queue::add_blocks(uint64_t height, uint64_t nblocks, const boost::uuids::uuid &connection_id, boost::posix_time::ptime time)
 {
+  CHECK_AND_ASSERT_THROW_MES(nblocks > 0, "Empty span");
   boost::unique_lock<boost::recursive_mutex> lock(mutex);
   blocks.insert(span(height, nblocks, connection_id, time));
 }
diff --git a/src/cryptonote_protocol/cryptonote_protocol_handler.inl b/src/cryptonote_protocol/cryptonote_protocol_handler.inl
index de30df5d7..8aef31a5a 100644
--- a/src/cryptonote_protocol/cryptonote_protocol_handler.inl
+++ b/src/cryptonote_protocol/cryptonote_protocol_handler.inl
@@ -1003,6 +1003,11 @@ skip:
           MDEBUG(context << " next span in the queue has blocks " << start_height << "-" << (start_height + blocks.size() - 1)
               << ", we need " << previous_height);
 
+          if (blocks.empty())
+          {
+            MERROR("Next span has no blocks");
+            break;
+          }
 
           block new_block;
           if (!parse_and_validate_block_from_blob(blocks.front().block, new_block))
@@ -1498,6 +1503,7 @@ skip:
 
       NOTIFY_REQUEST_CHAIN::request r = boost::value_initialized<NOTIFY_REQUEST_CHAIN::request>();
       m_core.get_short_chain_history(r.block_ids);
+      CHECK_AND_ASSERT_MES(!r.block_ids.empty(), false, "Short chain history is empty");
 
       if (!start_from_current_chain)
       {
diff --git a/src/mnemonics/electrum-words.cpp b/src/mnemonics/electrum-words.cpp
index 1b14905f6..ba67952aa 100644
--- a/src/mnemonics/electrum-words.cpp
+++ b/src/mnemonics/electrum-words.cpp
@@ -205,6 +205,8 @@ namespace
    */
   bool checksum_test(std::vector<std::string> seed, uint32_t unique_prefix_length)
   {
+    if (seed.empty())
+      return false;
     // The last word is the checksum.
     std::string last_word = seed.back();
     seed.pop_back();
diff --git a/src/rpc/core_rpc_server.cpp b/src/rpc/core_rpc_server.cpp
index a1d4d2d38..a6109cb89 100644
--- a/src/rpc/core_rpc_server.cpp
+++ b/src/rpc/core_rpc_server.cpp
@@ -492,6 +492,11 @@ namespace cryptonote
         {
           if (std::find(missed_txs.begin(), missed_txs.end(), h) == missed_txs.end())
           {
+            if (txs.empty())
+            {
+              res.status = "Failed: internal error - txs is empty";
+              return true;
+            }
             // core returns the ones it finds in the right order
             if (get_transaction_hash(txs.front()) != h)
             {
@@ -1150,7 +1155,7 @@ namespace cryptonote
       error_resp.message = "Internal error: can't get block by hash. Hash = " + req.hash + '.';
       return false;
     }
-    if (blk.miner_tx.vin.front().type() != typeid(txin_gen))
+    if (blk.miner_tx.vin.size() != 1 || blk.miner_tx.vin.front().type() != typeid(txin_gen))
     {
       error_resp.code = CORE_RPC_ERROR_CODE_INTERNAL_ERROR;
       error_resp.message = "Internal error: coinbase transaction in the block has the wrong type";
@@ -1188,7 +1193,7 @@ namespace cryptonote
         error_resp.message = "Internal error: can't get block by height. Height = " + boost::lexical_cast<std::string>(h) + ". Hash = " + epee::string_tools::pod_to_hex(block_hash) + '.';
         return false;
       }
-      if (blk.miner_tx.vin.front().type() != typeid(txin_gen))
+      if (blk.miner_tx.vin.size() != 1 || blk.miner_tx.vin.front().type() != typeid(txin_gen))
       {
         error_resp.code = CORE_RPC_ERROR_CODE_INTERNAL_ERROR;
         error_resp.message = "Internal error: coinbase transaction in the block has the wrong type";
@@ -1274,7 +1279,7 @@ namespace cryptonote
       error_resp.message = "Internal error: can't get block by hash. Hash = " + req.hash + '.';
       return false;
     }
-    if (blk.miner_tx.vin.front().type() != typeid(txin_gen))
+    if (blk.miner_tx.vin.size() != 1 || blk.miner_tx.vin.front().type() != typeid(txin_gen))
     {
       error_resp.code = CORE_RPC_ERROR_CODE_INTERNAL_ERROR;
       error_resp.message = "Internal error: coinbase transaction in the block has the wrong type";
diff --git a/src/rpc/daemon_handler.cpp b/src/rpc/daemon_handler.cpp
index 6643ce4e4..908f9e187 100644
--- a/src/rpc/daemon_handler.cpp
+++ b/src/rpc/daemon_handler.cpp
@@ -799,6 +799,10 @@ namespace rpc
     }
 
     header.hash = hash_in;
+    if (b.miner_tx.vin.size() != 1 || b.miner_tx.vin.front().type() != typeid(txin_gen))
+    {
+      return false;
+    }
     header.height = boost::get<txin_gen>(b.miner_tx.vin.front()).height;
 
     header.major_version = b.major_version;
diff --git a/src/simplewallet/simplewallet.cpp b/src/simplewallet/simplewallet.cpp
index 64e665fb3..e34e718d2 100644
--- a/src/simplewallet/simplewallet.cpp
+++ b/src/simplewallet/simplewallet.cpp
@@ -4321,9 +4321,9 @@ bool simple_wallet::sweep_single(const std::vector<std::string> &args_)
       fail_msg_writer() << tr("Multiple transactions are created, which is not supposed to happen");
       return true;
     }
-    if (ptx_vector[0].selected_transfers.size() > 1)
+    if (ptx_vector[0].selected_transfers.size() != 1)
     {
-      fail_msg_writer() << tr("The transaction uses multiple inputs, which is not supposed to happen");
+      fail_msg_writer() << tr("The transaction uses multiple or no inputs, which is not supposed to happen");
       return true;
     }
 
diff --git a/src/wallet/wallet2.cpp b/src/wallet/wallet2.cpp
index 04c6ee236..88f9e0934 100644
--- a/src/wallet/wallet2.cpp
+++ b/src/wallet/wallet2.cpp
@@ -4950,6 +4950,7 @@ bool wallet2::tx_add_fake_output(std::vector<std::vector<tools::wallet2::get_out
   if (global_index == real_index) // don't re-add real one
     return false;
   auto item = std::make_tuple(global_index, tx_public_key, mask);
+  CHECK_AND_ASSERT_MES(!outs.empty(), false, "internal error: outs is empty");
   if (std::find(outs.back().begin(), outs.back().end(), item) != outs.back().end()) // don't add duplicates
     return false;
   outs.back().push_back(item);
diff --git a/src/wallet/wallet_rpc_server.cpp b/src/wallet/wallet_rpc_server.cpp
index 0482b9dd6..baf8086f8 100644
--- a/src/wallet/wallet_rpc_server.cpp
+++ b/src/wallet/wallet_rpc_server.cpp
@@ -602,6 +602,13 @@ namespace tools
       uint64_t mixin = m_wallet->adjust_mixin(req.mixin);
       std::vector<wallet2::pending_tx> ptx_vector = m_wallet->create_transactions_2(dsts, mixin, req.unlock_time, req.priority, extra, req.account_index, req.subaddr_indices, m_trusted_daemon);
 
+      if (ptx_vector.empty())
+      {
+        er.code = WALLET_RPC_ERROR_CODE_TX_NOT_POSSIBLE;
+        er.message = "No transaction created";
+        return false;
+      }
+
       // reject proposed transactions if there are more than one.  see on_transfer_split below.
       if (ptx_vector.size() != 1)
       {