Sure!
Users who experiment the same problem just need to flash the core using the bootloader-patch-update branch of the firmware:
git clone git@github.com:spark/firmware
cd firmware
git checkout bootloader-patch-update
cd core-firmware/build
Then enter usb dfu/bootloader mode and flash their Core by executing
dfu-util -d 1d50:607f -a 0 -s 0x08005000:leave -D core-firmware.bin
Is there a reason why that branch is not merged back into master? I think that it would help to avoid other users to get confused