diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8fbbba56d..724c9130d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -339,13 +339,10 @@ if( EC_OS_NAME MATCHES "windows" )
     # Suppress warnings about using 'insecure' functions. Fixing this would require changes all over
     # the codebase which would damage portability.
     ecbuild_add_c_flags("/D_CRT_SECURE_NO_WARNINGS")
-    ecbuild_add_cxx_flags("/D_CRT_SECURE_NO_WARNINGS")
     # Suppress warnings about using well-known C functions.
     ecbuild_add_c_flags("/D_CRT_NONSTDC_NO_DEPRECATE")
-    ecbuild_add_cxx_flags("/D_CRT_NONSTDC_NO_DEPRECATE")
     # Suppress C4267: warns about possible loss of data when converting 'size_t' to 'int'.
     ecbuild_add_c_flags("/wd4267")
-    ecbuild_add_cxx_flags("/wd4267")
 endif()
 
 ###############################################################################
diff --git a/src/grib_api_internal.h b/src/grib_api_internal.h
index 2492aa9a8..553a44374 100644
--- a/src/grib_api_internal.h
+++ b/src/grib_api_internal.h
@@ -96,6 +96,8 @@ extern "C" {
  #define mkdir(dirname, mode) _mkdir(dirname)
 
  #ifdef _MSC_VER
+  #define _CRT_SECURE_NO_WARNINGS
+  #define _CRT_NONSTDC_NO_DEPRECATE
   #define access(path, mode) _access(path, mode)
   #define chmod(path, mode) _chmod(path, mode)
   #define strdup(str) _strdup(str)