preprocessor bug?

#define SYSYEM LINUX



#if SYSTEM == LINUX
#define HDR "linux.h"
#elif SYSTEM == WINDOWS
#define HDR "windows.h"
#elif SYSTEM == C51
#define HDR "c51.h"
#else
#define HDR "default.h"
#endif
#include HDR


I would expect this to work, but I just keep getting "warning C322: unknown identifier" errors. whats wrong?