diff --git a/reactos/include/reactos/typedefs_host.h b/reactos/include/reactos/typedefs_host.h
index bf100830acd..be13306961b 100644
--- a/reactos/include/reactos/typedefs_host.h
+++ b/reactos/include/reactos/typedefs_host.h
@@ -21,13 +21,13 @@
#error Unknown compiler
#endif
-#ifndef __fastcall
+#if !defined(_MSC_VER) && !defined(__fastcall)
#define __fastcall __attribute__((fastcall))
#endif
-#ifndef __cdecl
+#if !defined(_MSC_VER) && !defined(__cdecl)
#define __cdecl __attribute__((cdecl))
#endif
-#ifndef __stdcall
+#if !defined(_MSC_VER) && !defined(__stdcall)
#define __stdcall __attribute__((stdcall))
#endif
diff --git a/reactos/tools/mkhive/mkhive.vcproj b/reactos/tools/mkhive/mkhive.vcproj
index 4d69557ba3a..b89794fe56f 100644
--- a/reactos/tools/mkhive/mkhive.vcproj
+++ b/reactos/tools/mkhive/mkhive.vcproj
@@ -62,7 +62,7 @@
/>