Newer 6.x kernels (I tried 6.5.0 and 6.8.0) seem to behave differently for stack() than e.g. 5,15,0, Test test/unittest/aggs/tst.stack.d FAILs on those 6.x kernels whereas it passes on 5.15.0. I am not sure yet why there is a difference, but Eugene, perhaps you can take a look into this? Kris