diff --git a/tl/expected.hpp b/tl/expected.hpp
index e00a248..a4d9d62 100644
--- a/tl/expected.hpp
+++ b/tl/expected.hpp
@@ -75,6 +75,7 @@
 // for non-copyable types
 #elif (defined(__GNUC__) && __GNUC__ < 8 &&                                                \
      !defined(__clang__))
+#ifdef _GLIBCXX_VECTOR
 #ifndef TL_GCC_LESS_8_TRIVIALLY_COPY_CONSTRUCTIBLE_MUTEX
 #define TL_GCC_LESS_8_TRIVIALLY_COPY_CONSTRUCTIBLE_MUTEX
 namespace tl {
@@ -87,6 +88,7 @@ namespace tl {
   }
 }
 #endif
+#endif
 
 #define TL_EXPECTED_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T)                                     \
   tl::detail::is_trivially_copy_constructible<T>