diff --git a/expected.hpp b/expected.hpp
index c1cd6cd..c764efe 100644
--- a/expected.hpp
+++ b/expected.hpp
@@ -69,7 +69,8 @@
 namespace tl {
 template <class T, class E> class expected;
 
-#ifndef TL_OPTIONAL_EXPECTED_MUTEX
+#ifndef TL_MONOSTATE_INPLACE_MUTEX
+#define TL_MONOSTATE_INPLACE_MUTEX
 /// \brief Used to represent an expected with no data
 class monostate {};
 
@@ -156,7 +157,8 @@ static constexpr unexpect_t unexpect{};
 
 /// \exclude
 namespace detail {
-#ifndef TL_OPTIONAL_EXPECTED_MUTEX
+#ifndef TL_TRAITS_MUTEX
+#define TL_TRAITS_MUTEX
 // C++14-style aliases for brevity
 template <class T> using remove_const_t = typename std::remove_const<T>::type;
 template <class T>