diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2fcdfff1..00b1b5c5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -274,6 +274,9 @@ if(MSVC)
     target_compile_options(spdlog PRIVATE "/Zc:__cplusplus")
     target_compile_options(spdlog_header_only INTERFACE "/Zc:__cplusplus")
     if(SPDLOG_MSVC_UTF8)
+            # fmt requires the /utf-8 flag with huilding with msvc.
+	    # see https://github.com/fmtlib/fmt/pull/4159 on why the additional
+            # "$<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:MSVC>>" are needed
 	    target_compile_options(spdlog PUBLIC $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:MSVC>>:/utf-8>)
 	    target_compile_options(spdlog_header_only INTERFACE $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:MSVC>>:/utf-8>)    
      endif()