diff --git a/db_stress_tool/db_stress_driver.cc b/db_stress_tool/db_stress_driver.cc
index 7ab9c5a9a..6bf46861f 100644
--- a/db_stress_tool/db_stress_driver.cc
+++ b/db_stress_tool/db_stress_driver.cc
@@ -73,26 +73,31 @@ bool RunStressTest(StressTest* stress) {
   fprintf(stdout, "%s Initializing worker threads\n",
           clock->TimeToString(now / 1000000).c_str());
 
-  ThreadState bg_thread(0, &shared);
-  ThreadState continuous_verification_thread(0, &shared);
+  shared.SetThreads(n);
+
+  if (FLAGS_compaction_thread_pool_adjust_interval > 0) {
+    shared.IncBgThreads();
+  }
+
+  if (FLAGS_compaction_thread_pool_adjust_interval > 0) {
+    shared.IncBgThreads();
+  }
+
   std::vector<ThreadState*> threads(n);
-  {
-    MutexLock l(shared.GetMutex());
+  for (uint32_t i = 0; i < n; i++) {
+    threads[i] = new ThreadState(i, &shared);
+    db_stress_env->StartThread(ThreadBody, threads[i]);
+  }
 
-    for (uint32_t i = 0; i < n; i++) {
-      shared.IncThreads();
-      threads[i] = new ThreadState(i, &shared);
-      db_stress_env->StartThread(ThreadBody, threads[i]);
-    }
-    if (FLAGS_compaction_thread_pool_adjust_interval > 0) {
-      shared.IncBgThreads();
-      db_stress_env->StartThread(PoolSizeChangeThread, &bg_thread);
-    }
-    if (FLAGS_continuous_verification_interval > 0) {
-      shared.IncBgThreads();
-      db_stress_env->StartThread(DbVerificationThread,
-                                 &continuous_verification_thread);
-    }
+  ThreadState bg_thread(0, &shared);
+  if (FLAGS_compaction_thread_pool_adjust_interval > 0) {
+    db_stress_env->StartThread(PoolSizeChangeThread, &bg_thread);
+  }
+
+  ThreadState continuous_verification_thread(0, &shared);
+  if (FLAGS_continuous_verification_interval > 0) {
+    db_stress_env->StartThread(DbVerificationThread,
+                               &continuous_verification_thread);
   }
 
   // Each thread goes through the following states:
diff --git a/db_stress_tool/db_stress_shared_state.h b/db_stress_tool/db_stress_shared_state.h
index d48aeb131..ddfb67261 100644
--- a/db_stress_tool/db_stress_shared_state.h
+++ b/db_stress_tool/db_stress_shared_state.h
@@ -191,7 +191,7 @@ class SharedState {
 
   uint32_t GetNumThreads() const { return num_threads_; }
 
-  void IncThreads() { num_threads_++; }
+  void SetThreads(int num_threads) { num_threads_ = num_threads; }
 
   void IncInitialized() { num_initialized_++; }