Complication placeholder not showing

I've just added a complication to my watchOS app. I was able to select it on simulator's watch face, but it shows blank items. Temporary all methods of CLKComplicationDataSource return nil. I've created a new assets group for complication, added all required .png images as specified here, setup Complication Group property in Xcode target, but nothing shows up!

What should I do to enable static placeholder images for my complications?

Configuration in Xcode:

The problem was that the .xcassets file with placeholder images must be included into the watch extension bundle, but it was included into the watch app instead. I spend all day trying to figure this out.