diff --git a/src/pipeline.cc b/src/pipeline.cc
index 78ecde80..3fa887ba 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -423,6 +423,7 @@ void ThreadLeave() {
   std::lock_guard lock(thread_mtx);
   if (!--pending_threads)
     no_pending_threads.notify_one();
+  assert(pending_threads >= 0);
 }
 
 void Init() {
@@ -526,13 +527,13 @@ void LaunchStdin() {
       ReflectMember(reader, "method", method);
       if (method.empty())
         continue;
+      const auto should_exit = method == "exit";
       // g_config is not available before "initialize". Use 0 in that case.
       on_request->PushBack(
           {id, std::move(method), std::move(message), std::move(document),
            chrono::steady_clock::now() +
                chrono::milliseconds(g_config ? g_config->request.timeout : 0)});
-
-      if (method == "exit")
+      if (should_exit)
         break;
     }
   }).detach();
diff --git a/src/sema_manager.cc b/src/sema_manager.cc
index 585319e6..61542ef1 100644
--- a/src/sema_manager.cc
+++ b/src/sema_manager.cc
@@ -406,6 +406,10 @@ void BuildPreamble(Session &session, CompilerInvocation &CI,
 
 void *PreambleMain(void *manager_) {
   auto *manager = static_cast<SemaManager *>(manager_);
+  pipeline::ThreadEnter();
+  struct RAII {
+    ~RAII() { pipeline::ThreadLeave(); }
+  } raii{};
   set_thread_name("preamble");
   while (true) {
     SemaManager::PreambleTask task = manager->preamble_tasks.Dequeue();
@@ -432,12 +436,15 @@ void *PreambleMain(void *manager_) {
         manager->ScheduleDiag(task.path, debounce);
     }
   }
-  pipeline::ThreadLeave();
   return nullptr;
 }
 
 void *CompletionMain(void *manager_) {
   auto *manager = static_cast<SemaManager *>(manager_);
+  pipeline::ThreadEnter();
+  struct RAII {
+    ~RAII() { pipeline::ThreadLeave(); }
+  } raii{};
   set_thread_name("comp");
   while (true) {
     std::unique_ptr<SemaManager::CompTask> task = manager->comp_tasks.Dequeue();
@@ -493,7 +500,6 @@ void *CompletionMain(void *manager_) {
 
     task->on_complete(&Clang->getCodeCompletionConsumer());
   }
-  pipeline::ThreadLeave();
   return nullptr;
 }
 
@@ -527,6 +533,10 @@ void printDiag(llvm::raw_string_ostream &OS, const DiagBase &d) {
 
 void *DiagnosticMain(void *manager_) {
   auto *manager = static_cast<SemaManager *>(manager_);
+  pipeline::ThreadEnter();
+  struct RAII {
+    ~RAII() { pipeline::ThreadLeave(); }
+  } raii{};
   set_thread_name("diag");
   while (true) {
     SemaManager::DiagTask task = manager->diag_tasks.Dequeue();
@@ -643,7 +653,6 @@ void *DiagnosticMain(void *manager_) {
     }
     manager->on_diagnostic_(task.path, ls_diags);
   }
-  pipeline::ThreadLeave();
   return nullptr;
 }