filtered from NaN total entries not displaying

I have DataTables working using server side data. The basic part of the page information is displaying properly though I cannot get the filtered count to work properly (see the NaN below).

Showing 1 to 2 of 2 entries (filtered from NaN total entries)

According to the documentation I assumed this value should be populated from the server side iTotalDisplayRecords value. Is this correct or am I missing something?

The entries is being picked up properly from the iTotalDisplay value in the response. An except from my JSON response is below.

{"iTotalDisplay": 140, "iTotalDisplayRecords": 2, "aaData": [{"...

I am basing this on the following documentation page:

http://datatables.net/usage/server-side

int iTotalDisplayRecords Total records, after filtering (i.e. the total number of records after filtering has been applied - not just the number of records being returned in this result set)