diff --git a/src/optional.cpp b/src/optional.cpp
index b614d81..8c5dd76 100644
--- a/src/optional.cpp
+++ b/src/optional.cpp
@@ -9,8 +9,7 @@
 
 #include "experimental/optional"
 
-namespace std  // purposefully not using versioning namespace
-{ namespace experimental {
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 
 #ifdef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
 
@@ -22,4 +21,4 @@
 
 #endif
 
-}}  // std::experimental
+_LIBCPP_END_NAMESPACE_EXPERIMENTAL