diff --git a/test/constexpr_tests.hpp b/test/constexpr_tests.hpp
index 636a4e9..abe73a2 100644
--- a/test/constexpr_tests.hpp
+++ b/test/constexpr_tests.hpp
@@ -667,7 +667,7 @@ testConstantEvaluation()
 #endif
 }
 
-#ifdef BOOST_STATIC_STRING_CPP20
+#if __cpp_nontype_template_args >= 201911L
 
 template<basic_static_string<32, char, cxper_char_traits> X>
 struct nttp_primary