diff --git a/include/nlohmann/detail/json_custom_base_class.hpp b/include/nlohmann/detail/json_custom_base_class.hpp
index 1c278e4a1..f749c25e2 100644
--- a/include/nlohmann/detail/json_custom_base_class.hpp
+++ b/include/nlohmann/detail/json_custom_base_class.hpp
@@ -2,8 +2,7 @@
 
 #include <type_traits> // conditional, is_same
 
-namespace nlohmann
-{
+NLOHMANN_JSON_NAMESPACE_BEGIN
 namespace detail
 {