Dropping key_as_string from responses

I've been reading this thread, https://groups.google.com/forum/#!msg/elasticsearch/3e_4Y_1Ven4/F4Jf9T_1pUIJ trying to figure out how to remove key_as_string from my ES responses.

It seems this was fixed with this commit, https://github.com/elastic/elasticsearch/commit/2eb935544fe2dc9d327b4efa00ef97242d89d1db, but I cannot figure out how to utilize it. When i pass the format parameter ES tries to format the date; how do i ask it to do nothing?

my data is stored as "strict_date_optional_time||epoch_millis" and my query like so,

"aggs": {
    "day": {
        "date_histogram": {
        "field": "my_date",
        "interval": "day"

thank you for reading,