diff --git a/include/winbase.h b/include/winbase.h
index 4cae6eae3a9..adf7341136f 100644
--- a/include/winbase.h
+++ b/include/winbase.h
@@ -46,6 +46,8 @@ typedef DWORD (CALLBACK *LPTHREAD_START_ROUTINE)(LPVOID);
 typedef VOID (WINAPI *PFIBER_START_ROUTINE)( LPVOID lpFiberParameter );
 typedef PFIBER_START_ROUTINE LPFIBER_START_ROUTINE;
 
+#define FIBER_FLAG_FLOAT_SWITCH     1
+
 typedef RTL_CRITICAL_SECTION CRITICAL_SECTION;
 typedef PRTL_CRITICAL_SECTION PCRITICAL_SECTION;
 typedef PRTL_CRITICAL_SECTION LPCRITICAL_SECTION;