Calendar view does not respect "input required" exposed form style

I have a calendar view with two exposed filters. None of them is required, but I need users to select at least one, so I switched "Exposed form slyle" from "Basic" to "Input required". Without any input the view should display a simple message (see attachment), but it displays an empty calendar instead. It's sure going to confuse visitors and I don't have a chance to tell them what to do to get results.