diff --git a/llvm/include/llvm/Support/thread.h b/llvm/include/llvm/Support/thread.h
index ecde62d8368e7..51873e7d529bf 100644
--- a/llvm/include/llvm/Support/thread.h
+++ b/llvm/include/llvm/Support/thread.h
@@ -34,7 +34,7 @@ typedef PVOID HANDLE;
 
 namespace llvm {
 
-#if LLVM_ON_UNIX || _WIN32
+#if defined(LLVM_ON_UNIX) || defined(_WIN32)
 
 /// LLVM thread following std::thread interface with added constructor to
 /// specify stack size.
@@ -49,7 +49,7 @@ class thread {
   }
 
 public:
-#if LLVM_ON_UNIX
+#ifdef LLVM_ON_UNIX
   using native_handle_type = pthread_t;
   using id = pthread_t;
   using start_routine_type = void *(*)(void *);