diff --git a/config/flags/HDFMsvcFlags.cmake b/config/flags/HDFMsvcFlags.cmake
index db520fe..9ab9bde 100644
--- a/config/flags/HDFMsvcFlags.cmake
+++ b/config/flags/HDFMsvcFlags.cmake
@@ -25,5 +25,5 @@ if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 19.28)
 endif ()
 
 if(CMAKE_SYSTEM_PROCESSOR STREQUAL "ARM64" AND ${HDF_CFG_NAME} MATCHES "Debug")
-  set (WIN_COMPILE_FLAGS "${WIN_COMPILE_FLAGS} /Gy")
+  list (APPEND WIN_COMPILE_FLAGS "/Gy")
 endif ()