0 count facet values for date histogram?

Old Solr user, brand new ElasticSearch user. With Solr if I do date faceting and use a 24 hour range with a 1 hour gap, it'll return 24 results with the corresponding values, even if the value is 0, which is real useful when my goal is to take those numbers and toss them on a nice evenly spaced line chart. You sort of expect that if only 2 hours of the day had hits, that you'd have a long flatline with 2 spikes.

Can't quite figure out how to get ES to return me the 0 values. Is that possible or do I need to hand wedge them in?