diff --git a/CMakeLists.txt b/CMakeLists.txt
index 22db6470..6a0c2398 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -34,6 +34,11 @@ project (conjure_enum
    VERSION 1.0.0
 )
 
+# to enable conservative C++20 build:
+# cmake -DBUILD_CONSRVCPP20=true ..
+option(BUILD_CONSRVCPP20 "enable conservative C++20 build" false)
+message("-- Build conservative C++20: ${BUILD_CONSRVCPP20}")
+
 # to disable warnings:
 # cmake -DBUILD_ALL_WARNINGS=false ..
 option(BUILD_ALL_WARNINGS "enable building with all warnings" true)
@@ -65,6 +70,9 @@ foreach(x IN LISTS files)
 	add_executable(${target} examples/${x})
 	set_target_properties(${target} PROPERTIES CXX_STANDARD 20 CXX_STANDARD_REQUIRED true)
 	target_include_directories(${target} PRIVATE include)
+	if (BUILD_CONSRVCPP20)
+		target_compile_definitions(${target} PRIVATE BUILD_CONSRVCPP20)
+	endif()
 	if(BUILD_ALL_WARNINGS)
 		target_compile_options(${target} PRIVATE
 			$<$<CXX_COMPILER_ID:MSVC>:/W4>
diff --git a/include/fix8/conjure_enum.hpp b/include/fix8/conjure_enum.hpp
index c4ee4fcc..5546a658 100644
--- a/include/fix8/conjure_enum.hpp
+++ b/include/fix8/conjure_enum.hpp
@@ -192,7 +192,7 @@ class conjure_enum final
 			return false;
 	}
 
-#if defined(__clang__) && defined(__apple_build_version__) // std::count_if not constexpr in xcode/clang
+#if defined BUILD_CONSRVCPP20
 	template<std::size_t N>
 	static constexpr auto count_if_constexpr(const bool (&valid)[N]) noexcept
 	{
@@ -207,7 +207,7 @@ class conjure_enum final
 	template<std::size_t... I>
 	static constexpr auto _values(std::index_sequence<I...>) noexcept
 	{
-#if defined(__clang__) && defined(__apple_build_version__)
+#if defined BUILD_CONSRVCPP20
 		constexpr bool valid[sizeof...(I)] { _is_valid<static_cast<T>(enum_min_value + I)>()... };
 		constexpr auto num_valid { count_if_constexpr(valid) };
 #else