diff --git a/sys/winnt/windmain.c b/sys/winnt/windmain.c
index f88fbaa37..2cfab8c91 100644
--- a/sys/winnt/windmain.c
+++ b/sys/winnt/windmain.c
@@ -21,15 +21,17 @@ extern LONG GetCurrentPackageFullName(UINT32 *packageFullNameLength,
                       PWSTR  packageFullName);
 extern HRESULT SHGetKnownFolderPath(REFKNOWNFOLDERID rfid,
                       DWORD dwFlags, HANDLE hToken, PWSTR  *ppszPath);
+#ifndef DEFINE_KNOWN_FOLDER
 #ifdef INITGUID
 #define DEFINE_KNOWN_FOLDER(name, l, w1, w2, b1, b2, b3, b4, b5, b6, b7, b8) const GUID DECLSPEC_SELECTANY name = { l, w1, w2,{ b1, b2, b3, b4, b5, b6, b7, b8 } }
 #else
 #define DEFINE_KNOWN_FOLDER(name, l, w1, w2, b1, b2, b3, b4, b5, b6, b7, b8) const GUID name
-#endif
+#endif /* INITGUID */
+#endif /* DEFINE_KNOWN_FOLDER */
 DEFINE_KNOWN_FOLDER (FOLDERID_ProgramData, 0x62ab5d82, 0xfdc1, 0x4dc3, 0xa9, 0xdd, 0x07, 0x0d, 0x1d, 0x49, 0x5d, 0x97);
 DEFINE_KNOWN_FOLDER (FOLDERID_LocalAppData, 0xf1b32785, 0x6fba, 0x4fcf, 0x9d, 0x55, 0x7b, 0x8e, 0x7f, 0x15, 0x70, 0x91);
 DEFINE_KNOWN_FOLDER (FOLDERID_Profile, 0x5e6c858f, 0x0e22, 0x4760, 0x9a, 0xfe, 0xea, 0x33, 0x17, 0xb6, 0x71, 0x73);
-#endif
+#endif  /* __MINGW32__ */
 
 #if 0
 #include "wintty.h"