Can't use EventTime in vis of window Query

[stroomdev10]

from "blah"

eval p0=mask(0,count())
eval p1 = mak(1,count())

window EventTime by 1d

select p0,p1

show as LineChart(x=EventTime, y=p0)

This query automatically adds the EventTime field, but I can't use it in the show()

I can add eval EventTime = any(EventTime). and select it. , but I don't feel i should have to.