diff --git a/reactos/w32api/include/winnls.h b/reactos/w32api/include/winnls.h
index acdaf516c65..47463c974e2 100644
--- a/reactos/w32api/include/winnls.h
+++ b/reactos/w32api/include/winnls.h
@@ -29,6 +29,7 @@ extern "C" {
 #define LOCALE_IDEFAULTCOUNTRY	10
 #define LOCALE_IDEFAULTCODEPAGE	11
 #define LOCALE_IDEFAULTANSICODEPAGE 0x1004
+#define LOCALE_IDEFAULTMACCODEPAGE 0x1011
 #define LOCALE_SLIST	12
 #define LOCALE_IMEASURE	13
 #define LOCALE_SDECIMAL	14