https://bugs.winehq.org/show_bug.cgi?id=49395
--- Comment #4 from Henri Verbeet hverbeet@gmail.com --- (In reply to Shane from comment #2)
Aha, that helps! I didn't realise that you needed WINEDEBUG to print warnings. I did try it anyway, but I was doing WINEDEBUG=+d2d1, which made no difference.
Mostly for future reference, the default debug channel is declared with the WINE_DEFAULT_DEBUG_CHANNEL macro, typically near the top of the relevant file.