State timeline, Color Scheme: From Threshold -> Transparent not working

State-timeline diagram, yellow for value <> zero, transparent color else.
Color scheme: From thresholds by value.
Thresholds: Base: transparent, 1: yellow
See screenshot: “Zeros” are shown as Black. Only none values are shown transparent but zero values should be transparent, too.

Set No Value to “0” → no change.

Any idea?