diff --git a/src/test/test_bitcoin.cpp b/src/test/test_bitcoin.cpp
index cfa0dfda5..47d9d5b75 100644
--- a/src/test/test_bitcoin.cpp
+++ b/src/test/test_bitcoin.cpp
@@ -1,223 +1,223 @@
 // Copyright (c) 2011-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <test/test_bitcoin.h>
 
 #include <chain.h>
 #include <chainparams.h>
 #include <config.h>
 #include <consensus/consensus.h>
 #include <consensus/validation.h>
 #include <crypto/sha256.h>
 #include <fs.h>
 #include <key.h>
 #include <logging.h>
 #include <miner.h>
 #include <net_processing.h>
 #include <noui.h>
 #include <pubkey.h>
 #include <random.h>
 #include <rpc/register.h>
 #include <rpc/server.h>
 #include <script/scriptcache.h>
 #include <script/sigcache.h>
 #include <txdb.h>
 #include <txmempool.h>
 #include <ui_interface.h>
 #include <validation.h>
 
 #include <memory>
 
+FastRandomContext g_insecure_rand_ctx;
+
 void CConnmanTest::AddNode(CNode &node) {
     LOCK(g_connman->cs_vNodes);
     g_connman->vNodes.push_back(&node);
 }
 
 void CConnmanTest::ClearNodes() {
     LOCK(g_connman->cs_vNodes);
     g_connman->vNodes.clear();
 }
 
-thread_local FastRandomContext g_insecure_rand_ctx;
-
 std::ostream &operator<<(std::ostream &os, const uint256 &num) {
     os << num.ToString();
     return os;
 }
 
 BasicTestingSetup::BasicTestingSetup(const std::string &chainName)
     : m_path_root(fs::temp_directory_path() / "test_bitcoin" /
                   strprintf("%lu_%i", static_cast<unsigned long>(GetTime()),
                             int(InsecureRandRange(1 << 30)))) {
     SHA256AutoDetect();
     RandomInit();
     ECC_Start();
     SetupEnvironment();
     SetupNetworking();
     InitSignatureCache();
     InitScriptExecutionCache();
 
     // Don't want to write to debug.log file.
     GetLogger().m_print_to_file = false;
 
     fCheckBlockIndex = true;
     SelectParams(chainName);
     noui_connect();
 
     // Set config parameters to default.
     GlobalConfig config;
     config.SetMaxBlockSize(DEFAULT_MAX_BLOCK_SIZE);
 }
 
 BasicTestingSetup::~BasicTestingSetup() {
     fs::remove_all(m_path_root);
     ECC_Stop();
 }
 
 fs::path BasicTestingSetup::SetDataDir(const std::string &name) {
     fs::path ret = m_path_root / name;
     fs::create_directories(ret);
     gArgs.ForceSetArg("-datadir", ret.string());
     return ret;
 }
 
 TestingSetup::TestingSetup(const std::string &chainName)
     : BasicTestingSetup(chainName) {
     SetDataDir("tempdir");
     const Config &config = GetConfig();
     const CChainParams &chainparams = config.GetChainParams();
 
     // Ideally we'd move all the RPC tests to the functional testing framework
     // instead of unit tests, but for now we need these here.
     RPCServer rpcServer;
     RegisterAllRPCCommands(config, rpcServer, tableRPC);
 
     /**
      * RPC does not come out of the warmup state on its own. Normally, this is
      * handled in bitcoind's init path, but unit tests do not trigger this
      * codepath, so we call it explicitly as part of setup.
      */
     std::string rpcWarmupStatus;
     if (RPCIsInWarmup(&rpcWarmupStatus)) {
         SetRPCWarmupFinished();
     }
 
     ClearDatadirCache();
 
     // We have to run a scheduler thread to prevent ActivateBestChain
     // from blocking due to queue overrun.
     threadGroup.create_thread(
         boost::bind(&CScheduler::serviceQueue, &scheduler));
     GetMainSignals().RegisterBackgroundSignalScheduler(scheduler);
 
     g_mempool.setSanityCheck(1.0);
     pblocktree.reset(new CBlockTreeDB(1 << 20, true));
     pcoinsdbview.reset(new CCoinsViewDB(1 << 23, true));
     pcoinsTip.reset(new CCoinsViewCache(pcoinsdbview.get()));
     if (!LoadGenesisBlock(chainparams)) {
         throw std::runtime_error("LoadGenesisBlock failed.");
     }
     {
         CValidationState state;
         if (!ActivateBestChain(config, state)) {
             throw std::runtime_error("ActivateBestChain failed.");
         }
     }
     nScriptCheckThreads = 3;
     for (int i = 0; i < nScriptCheckThreads - 1; i++) {
         threadGroup.create_thread(&ThreadScriptCheck);
     }
 
     // Deterministic randomness for tests.
     g_connman = std::unique_ptr<CConnman>(new CConnman(config, 0x1337, 0x1337));
     connman = g_connman.get();
     peerLogic.reset(new PeerLogicValidation(connman, scheduler));
 }
 
 TestingSetup::~TestingSetup() {
     threadGroup.interrupt_all();
     threadGroup.join_all();
     GetMainSignals().FlushBackgroundCallbacks();
     GetMainSignals().UnregisterBackgroundSignalScheduler();
     g_connman.reset();
     peerLogic.reset();
     UnloadBlockIndex();
     pcoinsTip.reset();
     pcoinsdbview.reset();
     pblocktree.reset();
 }
 
 TestChain100Setup::TestChain100Setup()
     : TestingSetup(CBaseChainParams::REGTEST) {
     // Generate a 100-block chain:
     coinbaseKey.MakeNewKey(true);
     CScript scriptPubKey = CScript() << ToByteVector(coinbaseKey.GetPubKey())
                                      << OP_CHECKSIG;
     for (int i = 0; i < COINBASE_MATURITY; i++) {
         std::vector<CMutableTransaction> noTxns;
         CBlock b = CreateAndProcessBlock(noTxns, scriptPubKey);
         m_coinbase_txns.push_back(b.vtx[0]);
     }
 }
 
 //
 // Create a new block with just given transactions, coinbase paying to
 // scriptPubKey, and try to add it to the current chain.
 //
 CBlock TestChain100Setup::CreateAndProcessBlock(
     const std::vector<CMutableTransaction> &txns, const CScript &scriptPubKey) {
     const Config &config = GetConfig();
     std::unique_ptr<CBlockTemplate> pblocktemplate =
         BlockAssembler(config, g_mempool).CreateNewBlock(scriptPubKey);
     CBlock &block = pblocktemplate->block;
 
     // Replace mempool-selected txns with just coinbase plus passed-in txns:
     block.vtx.resize(1);
     for (const CMutableTransaction &tx : txns) {
         block.vtx.push_back(MakeTransactionRef(tx));
     }
 
     // Order transactions by canonical order
     std::sort(std::begin(block.vtx) + 1, std::end(block.vtx),
               [](const std::shared_ptr<const CTransaction> &txa,
                  const std::shared_ptr<const CTransaction> &txb) -> bool {
                   return txa->GetId() < txb->GetId();
               });
 
     // IncrementExtraNonce creates a valid coinbase and merkleRoot
     unsigned int extraNonce = 0;
     {
         LOCK(cs_main);
         IncrementExtraNonce(config, &block, chainActive.Tip(), extraNonce);
     }
 
     while (!CheckProofOfWork(block.GetHash(), block.nBits, config)) {
         ++block.nNonce;
     }
 
     std::shared_ptr<const CBlock> shared_pblock =
         std::make_shared<const CBlock>(block);
     ProcessNewBlock(GetConfig(), shared_pblock, true, nullptr);
 
     CBlock result = block;
     return result;
 }
 
 TestChain100Setup::~TestChain100Setup() {}
 
 CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(const CMutableTransaction &tx,
                                                CTxMemPool *pool) {
     return FromTx(MakeTransactionRef(tx), pool);
 }
 
 CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(const CTransactionRef &tx,
                                                CTxMemPool *pool) {
     // Hack to assume either it's completely dependent on other mempool txs or
     // not at all.
     Amount inChainValue =
         pool && pool->HasNoInputsOf(*tx) ? tx->GetValueOut() : Amount::zero();
 
     return CTxMemPoolEntry(tx, nFee, nTime, dPriority, nHeight, inChainValue,
                            spendsCoinbase, sigOpCost, lp);
 }
diff --git a/src/test/test_bitcoin.h b/src/test/test_bitcoin.h
index 4b7e4012e..09d80e75e 100644
--- a/src/test/test_bitcoin.h
+++ b/src/test/test_bitcoin.h
@@ -1,164 +1,171 @@
 // Copyright (c) 2015-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_TEST_TEST_BITCOIN_H
 #define BITCOIN_TEST_TEST_BITCOIN_H
 
 #include <chainparamsbase.h>
 #include <fs.h>
 #include <key.h>
 #include <pubkey.h>
 #include <random.h>
 #include <scheduler.h>
 #include <txmempool.h>
 
 /**
  * Version of Boost::test prior to 1.64 have issues when dealing with nullptr_t.
  * In order to work around this, we ensure that the null pointers are typed in a
  * way that Boost will like better.
  *
  * TODO: Use nullptr directly once the minimum version of boost is 1.64 or more.
  */
 #define NULLPTR(T) static_cast<T *>(nullptr)
 
-thread_local extern FastRandomContext g_insecure_rand_ctx;
+/**
+ * This global and the helpers that use it are not thread-safe.
+ *
+ * If thread-safety is needed, the global could be made thread_local (given
+ * that thread_local is supported on all architectures we support) or a
+ * per-thread instance could be used in the multi-threaded test.
+ */
+extern FastRandomContext g_insecure_rand_ctx;
 
 static inline void SeedInsecureRand(bool deterministic = false) {
     g_insecure_rand_ctx = FastRandomContext(deterministic);
 }
 
 static inline uint32_t InsecureRand32() {
     return g_insecure_rand_ctx.rand32();
 }
 static inline uint256 InsecureRand256() {
     return g_insecure_rand_ctx.rand256();
 }
 static inline uint64_t InsecureRandBits(int bits) {
     return g_insecure_rand_ctx.randbits(bits);
 }
 static inline uint64_t InsecureRandRange(uint64_t range) {
     return g_insecure_rand_ctx.randrange(range);
 }
 static inline bool InsecureRandBool() {
     return g_insecure_rand_ctx.randbool();
 }
 
 /**
  * Basic testing setup.
  * This just configures logging and chain parameters.
  */
 struct BasicTestingSetup {
     ECCVerifyHandle globalVerifyHandle;
 
     explicit BasicTestingSetup(
         const std::string &chainName = CBaseChainParams::MAIN);
     ~BasicTestingSetup();
 
     fs::path SetDataDir(const std::string &name);
 
 private:
     const fs::path m_path_root;
 };
 
 /**
  * Testing setup that configures a complete environment.
  * Included are data directory, coins database, script check threads setup.
  */
 class CConnman;
 class CNode;
 struct CConnmanTest {
     static void AddNode(CNode &node);
     static void ClearNodes();
 };
 
 class PeerLogicValidation;
 struct TestingSetup : public BasicTestingSetup {
     boost::thread_group threadGroup;
     CConnman *connman;
     CScheduler scheduler;
     std::unique_ptr<PeerLogicValidation> peerLogic;
 
     explicit TestingSetup(
         const std::string &chainName = CBaseChainParams::MAIN);
     ~TestingSetup();
 };
 
 class CBlock;
 class CMutableTransaction;
 class CScript;
 
 //
 // Testing fixture that pre-creates a
 // 100-block REGTEST-mode block chain
 //
 struct TestChain100Setup : public TestingSetup {
     TestChain100Setup();
 
     // Create a new block with just given transactions, coinbase paying to
     // scriptPubKey, and try to add it to the current chain.
     CBlock CreateAndProcessBlock(const std::vector<CMutableTransaction> &txns,
                                  const CScript &scriptPubKey);
 
     ~TestChain100Setup();
 
     // For convenience, coinbase transactions.
     std::vector<CTransactionRef> m_coinbase_txns;
     // private/public key needed to spend coinbase transactions.
     CKey coinbaseKey;
 };
 
 class CTxMemPoolEntry;
 class CTxMemPool;
 
 struct TestMemPoolEntryHelper {
     // Default values
     Amount nFee;
     int64_t nTime;
     double dPriority;
     unsigned int nHeight;
     bool spendsCoinbase;
     unsigned int sigOpCost;
     LockPoints lp;
 
     TestMemPoolEntryHelper()
         : nFee(), nTime(0), dPriority(0.0), nHeight(1), spendsCoinbase(false),
           sigOpCost(4) {}
 
     CTxMemPoolEntry FromTx(const CMutableTransaction &tx,
                            CTxMemPool *pool = nullptr);
     CTxMemPoolEntry FromTx(const CTransactionRef &tx,
                            CTxMemPool *pool = nullptr);
 
     // Change the default value
     TestMemPoolEntryHelper &Fee(Amount _fee) {
         nFee = _fee;
         return *this;
     }
     TestMemPoolEntryHelper &Time(int64_t _time) {
         nTime = _time;
         return *this;
     }
     TestMemPoolEntryHelper &Priority(double _priority) {
         dPriority = _priority;
         return *this;
     }
     TestMemPoolEntryHelper &Height(unsigned int _height) {
         nHeight = _height;
         return *this;
     }
     TestMemPoolEntryHelper &SpendsCoinbase(bool _flag) {
         spendsCoinbase = _flag;
         return *this;
     }
     TestMemPoolEntryHelper &SigOpsCost(unsigned int _sigopsCost) {
         sigOpCost = _sigopsCost;
         return *this;
     }
 };
 
 // define an implicit conversion here so that uint256 may be used directly in
 // BOOST_CHECK_*
 std::ostream &operator<<(std::ostream &os, const uint256 &num);
 
 #endif
diff --git a/src/test/validation_block_tests.cpp b/src/test/validation_block_tests.cpp
index 609061981..57a35b1c2 100644
--- a/src/test/validation_block_tests.cpp
+++ b/src/test/validation_block_tests.cpp
@@ -1,203 +1,206 @@
 // Copyright (c) 2018 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <boost/test/unit_test.hpp>
 
 #include <chain.h>
 #include <chainparams.h>
 #include <config.h>
 #include <consensus/merkle.h>
 #include <consensus/validation.h>
 #include <miner.h>
 #include <pow.h>
 #include <random.h>
 #include <test/test_bitcoin.h>
 #include <utiltime.h>
 #include <validation.h>
 #include <validationinterface.h>
 
 struct RegtestingSetup : public TestingSetup {
     RegtestingSetup() : TestingSetup(CBaseChainParams::REGTEST) {}
 };
 
 BOOST_FIXTURE_TEST_SUITE(validation_block_tests, RegtestingSetup)
 
 struct TestSubscriber : public CValidationInterface {
     uint256 m_expected_tip;
 
     TestSubscriber(uint256 tip) : m_expected_tip(tip) {}
 
     void UpdatedBlockTip(const CBlockIndex *pindexNew,
                          const CBlockIndex *pindexFork, bool fInitialDownload) {
         BOOST_CHECK_EQUAL(m_expected_tip, pindexNew->GetBlockHash());
     }
 
     void BlockConnected(const std::shared_ptr<const CBlock> &block,
                         const CBlockIndex *pindex,
                         const std::vector<CTransactionRef> &txnConflicted) {
         BOOST_CHECK_EQUAL(m_expected_tip, block->hashPrevBlock);
         BOOST_CHECK_EQUAL(m_expected_tip, pindex->pprev->GetBlockHash());
 
         m_expected_tip = block->GetHash();
     }
 
     void BlockDisconnected(const std::shared_ptr<const CBlock> &block) {
         BOOST_CHECK_EQUAL(m_expected_tip, block->GetHash());
 
         m_expected_tip = block->hashPrevBlock;
     }
 };
 
 std::shared_ptr<CBlock> Block(const Config &config, const uint256 &prev_hash) {
     static int i = 0;
     static uint64_t time = config.GetChainParams().GenesisBlock().nTime;
 
     CScript pubKey;
     pubKey << i++ << OP_TRUE;
 
     auto ptemplate = BlockAssembler(config, g_mempool).CreateNewBlock(pubKey);
     auto pblock = std::make_shared<CBlock>(ptemplate->block);
     pblock->hashPrevBlock = prev_hash;
     pblock->nTime = ++time;
 
     CMutableTransaction txCoinbase(*pblock->vtx[0]);
     txCoinbase.vout.resize(1);
     pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
 
     return pblock;
 }
 
 std::shared_ptr<CBlock> FinalizeBlock(const Config &config,
                                       std::shared_ptr<CBlock> pblock) {
     pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
 
     while (!CheckProofOfWork(pblock->GetHash(), pblock->nBits, config)) {
         ++(pblock->nNonce);
     }
 
     return pblock;
 }
 
 // construct a valid block
 const std::shared_ptr<const CBlock> GoodBlock(const Config &config,
                                               const uint256 &prev_hash) {
     return FinalizeBlock(config, Block(config, prev_hash));
 }
 
 // construct an invalid block (but with a valid header)
 const std::shared_ptr<const CBlock> BadBlock(const Config &config,
                                              const uint256 &prev_hash) {
     auto pblock = Block(config, prev_hash);
 
     CMutableTransaction coinbase_spend;
     coinbase_spend.vin.push_back(
         CTxIn(COutPoint(pblock->vtx[0]->GetHash(), 0), CScript(), 0));
     coinbase_spend.vout.push_back(pblock->vtx[0]->vout[0]);
 
     CTransactionRef tx = MakeTransactionRef(coinbase_spend);
     pblock->vtx.push_back(tx);
 
     auto ret = FinalizeBlock(config, pblock);
     return ret;
 }
 
 void BuildChain(const Config &config, const uint256 &root, int height,
                 const unsigned int invalid_rate, const unsigned int branch_rate,
                 const unsigned int max_size,
                 std::vector<std::shared_ptr<const CBlock>> &blocks) {
     if (height <= 0 || blocks.size() >= max_size) {
         return;
     }
 
     bool gen_invalid = InsecureRandRange(100) < invalid_rate;
     bool gen_fork = InsecureRandRange(100) < branch_rate;
 
     const std::shared_ptr<const CBlock> pblock =
         gen_invalid ? BadBlock(config, root) : GoodBlock(config, root);
     blocks.push_back(pblock);
     if (!gen_invalid) {
         BuildChain(config, pblock->GetHash(), height - 1, invalid_rate,
                    branch_rate, max_size, blocks);
     }
 
     if (gen_fork) {
         blocks.push_back(GoodBlock(config, root));
         BuildChain(config, blocks.back()->GetHash(), height - 1, invalid_rate,
                    branch_rate, max_size, blocks);
     }
 }
 
 BOOST_AUTO_TEST_CASE(processnewblock_signals_ordering) {
     GlobalConfig config;
     const CChainParams &chainParams = config.GetChainParams();
 
     // build a large-ish chain that's likely to have some forks
     std::vector<std::shared_ptr<const CBlock>> blocks;
     while (blocks.size() < 50) {
         blocks.clear();
         BuildChain(config, chainParams.GenesisBlock().GetHash(), 100, 15, 10,
                    500, blocks);
     }
 
     bool ignored;
     CValidationState state;
     std::vector<CBlockHeader> headers;
     std::transform(
         blocks.begin(), blocks.end(), std::back_inserter(headers),
         [](std::shared_ptr<const CBlock> b) { return b->GetBlockHeader(); });
 
     // Process all the headers so we understand the toplogy of the chain
     BOOST_CHECK(ProcessNewBlockHeaders(config, headers, state));
 
     // Connect the genesis block and drain any outstanding events
     ProcessNewBlock(config,
                     std::make_shared<CBlock>(chainParams.GenesisBlock()), true,
                     &ignored);
     SyncWithValidationInterfaceQueue();
 
     // subscribe to events (this subscriber will validate event ordering)
     const CBlockIndex *initial_tip = nullptr;
     {
         LOCK(cs_main);
         initial_tip = chainActive.Tip();
     }
     TestSubscriber sub(initial_tip->GetBlockHash());
     RegisterValidationInterface(&sub);
 
     // create a bunch of threads that repeatedly process a block generated above
     // at random this will create parallelism and randomness inside validation -
     // the ValidationInterface will subscribe to events generated during block
     // validation and assert on ordering invariance
-    boost::thread_group threads;
+    std::vector<std::thread> threads;
     for (int i = 0; i < 10; i++) {
-        threads.create_thread([&config, &blocks]() {
+        threads.emplace_back([&config, &blocks]() {
             bool tlignored;
+            FastRandomContext insecure;
             for (int j = 0; j < 1000; j++) {
-                auto block = blocks[InsecureRandRange(blocks.size() - 1)];
+                auto block = blocks[insecure.randrange(blocks.size() - 1)];
                 ProcessNewBlock(config, block, true, &tlignored);
             }
 
             // to make sure that eventually we process the full chain - do it
             // here
             for (auto block : blocks) {
                 if (block->vtx.size() == 1) {
                     bool processed =
                         ProcessNewBlock(config, block, true, &tlignored);
                     assert(processed);
                 }
             }
         });
     }
 
-    threads.join_all();
+    for (auto &t : threads) {
+        t.join();
+    }
     while (GetMainSignals().CallbacksPending() > 0) {
         MilliSleep(100);
     }
 
     UnregisterValidationInterface(&sub);
 
     BOOST_CHECK_EQUAL(sub.m_expected_tip, chainActive.Tip()->GetBlockHash());
 }
 
 BOOST_AUTO_TEST_SUITE_END()