no "captured output" under files/ErrorLogs when running tests via REST interface

when running tests via the REST interface (either ?test&format=text or format=xml) there is no captured output written to the ErrorLogs dir. IIRC those logs were written when running tests via CLI. I prefer the REST interface over using the CLI since parallelization via xargs and curl works more stable for us as it did with the CLI.
Am i missing an additional needed argument to get the logs or is this a bug in fitnesse?

best regards, 
chris