diff --git a/Source/Platform.h b/Source/Platform.h
index 23f63852..c0f98a01 100644
--- a/Source/Platform.h
+++ b/Source/Platform.h
@@ -468,6 +468,7 @@ typedef DWORDLONG ULONGLONG,*PULONGLONG;
 #  define MB_ICONQUESTION 32
 #  define MB_ICONEXCLAMATION 48
 #  define MB_ICONINFORMATION 64
+#  define MB_USERICON 128
 #  define MB_SETFOREGROUND 0x10000
 #  define MB_TOPMOST 0x40000
 #  define MB_RIGHT 0x80000