icewm+xcompmgr

[Sasha <sas...@bk...>]

using icewm-1.2.37 + xcompmgr-1.1.4 + transset-df-6_1, xorg 7.4
i've came upon some artefact:
with transparency set invisible parts of window decoration
save background  and become visible while moving windows
(screenshot attached)

is it a bug, or i've missed some tricky option in config?

i've tryed different themes and totally commented ./icewm/preferences
- artefact remains
//