How to avoid Qt Test from timing out after 600s

Is it possible to ignore the MAX_VALUE of 600 sec at Qt-testing? I try:

qputenv("QTEST_FUNCTION_TIMEOUT", "1000000"); // 1'000 sec

but the result is:

System.Exception: Process timed out: 600s

So it is possible to increase the timeout from 300s to 600s. The problem is, I need in one case 800 sec, how can I realize that?

Setting timeout to Qt Test