diff --git a/src/cuda/api/detail/optional.hpp b/src/cuda/api/detail/optional.hpp
index a59559c2..20b55fb1 100644
--- a/src/cuda/api/detail/optional.hpp
+++ b/src/cuda/api/detail/optional.hpp
@@ -15,9 +15,9 @@ using ::std::optional;
 using ::std::nullopt;
 } // namespace cuda
 #elif __cplusplus >= 201402L
-namespace cuda {
 #include <experimental/optional>
 #include <experimental/any>
+namespace cuda {
 using ::std::experimental::optional;
 using ::std::experimental::nullopt;
 } // namespace cuda