Px4iofirmware doesn't recompile after it has been edited

Hey guys.
I have edited the px4iofirmware.cpp for my FMU-V5’s IO in v1.13.0 master. However it still says "INFO [px4io] IO FW CRC match" after the firmware updated and rebooted. Why? Shouldn’t the io’s firmware be updated automatically after it has been reedited?
How could I update the IO’s firmware after the change of the IO’s firmware? It seems like the compilation just uses the px4_io-v2_default.bin directly from somewhere without recompiles it again although I do have changed the px4iofirmware.cpp .