AVR 231 Bootloader GCC

Hallo,

weiß jemand wieso bei diesem Code:

union
{
    struct
    {
        uint8_t m_rxBuffer[BUFFER_SIZE];            // Receive buffer
        uint8_t m_pageBuffer[PAGE_SIZE];            // Page is assembled 
here before
                                                    // getting 
programmed to flash memory
    } part1;

#if KEY_COUNT > 0
    struct
    {
        uint8_t m_tempbuf[256];                     // Temp buffer for 
aesInit.
    } part2;
#endif
} sharedbufs;

diese Fehlermeldung entsteht:

../loader.c:85: error: size of variable 'sharedbufs' is too large

?