The official format for a Binary object is {{

{"$binary": "<bindata>", "$type": "<t>"}

}} (the type is a two-char hex string) [ref], but json_util uses {{

{"$binary": "<bindata>", "$type": <t>}

}} (the type is an integer) instead.

I noticed this bug when trying to read the output of mongoexport from Python.

I've attached a patch to fix this bug. The patch also updates the doctests in the json_util module.

This change will break any code that has stored the broken JSON anywhere and then reads it back after updating.