#if USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER == 0 && USB_CFG_SERIAL_NUMBER_LEN
#undef USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER
#define USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER sizeof(usbDescriptorStringSerialNumber)
-PROGMEM int usbDescriptorStringSerialNumber[] = {
+const PROGMEM int usbDescriptorStringSerialNumber[] = {
USB_STRING_DESCRIPTOR_HEADER(USB_CFG_SERIAL_NUMBER_LEN),
USB_CFG_SERIAL_NUMBER
};