diff --git a/src/test/test_bitcoin.h b/src/test/test_bitcoin.h
--- a/src/test/test_bitcoin.h
+++ b/src/test/test_bitcoin.h
@@ -22,7 +22,14 @@
  */
 #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);
diff --git a/src/test/test_bitcoin.cpp b/src/test/test_bitcoin.cpp
--- a/src/test/test_bitcoin.cpp
+++ b/src/test/test_bitcoin.cpp
@@ -29,6 +29,8 @@
 
 #include <memory>
 
+FastRandomContext g_insecure_rand_ctx;
+
 void CConnmanTest::AddNode(CNode &node) {
     LOCK(g_connman->cs_vNodes);
     g_connman->vNodes.push_back(&node);
@@ -39,8 +41,6 @@
     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;
diff --git a/src/test/validation_block_tests.cpp b/src/test/validation_block_tests.cpp
--- a/src/test/validation_block_tests.cpp
+++ b/src/test/validation_block_tests.cpp
@@ -169,12 +169,13 @@
     // 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);
             }
 
@@ -190,7 +191,9 @@
         });
     }
 
-    threads.join_all();
+    for (auto &t : threads) {
+        t.join();
+    }
     while (GetMainSignals().CallbacksPending() > 0) {
         MilliSleep(100);
     }