Thanks @bko for posting a possible solution.
However, the error unfortunately remains. I will do some extra googling to see if there is other possible solutions on that.
There are more people who had the same issue with the spark-osc firmware.
Possibly it’s something that has to do with the firmware itself, because it compiles correctly with the firmware v.0.2.1 (but when I flash it on the spark.io it just get’s stuck on DFU mode, not responding on anything)