Cant set sequential_cutoff

[Jonny <johnny@xxxxxxxxxxxxxxxxxxx>]

Bcache is up and seems running, bcache-state is clean.

cat /sys/block/bcache0/bcache/sequential_cutoff
0.0k

This should not return 0.0k?
I tried to set it back to 4M, but get the following Error:

echo 4M > /sys/block/bcache0/bcache/sequential_cutoff
bash: echo: write error: Invalid argument


Thanks in Advance