Ahh, I discovered a trick that solves it for me.
The end time on the last day of the event has to be set to 9:00am or later. (I had been using the “All day” checkbox with the default time of midnight on both ends. Then I played around with various end times, and it seemed that 9:00am was the magic cut-off point.) It would be nice, though, if in the next release we could just click the “all day” button and have the bar span through the last day.