Not handling nulls like in Mongo

[datanotion]

Does meteor-aggregate handle a ​_null_​ in an aggregate query different than native Mongo? I have a query that runs fine in Mongo, but returns no records in Meteor using this library. Once I remove the match on a field that is Null in the database, it runs just fine.

Super-simplifed version of the query:

db.expenses.aggregate(
[
{"$match":{
"details.account_number":10940,
"details.vendor_id":null,
"details.dept_id":1}
}
]
)

But once I remove the vendor_id match, then Meteor returns the records.

Is this a bug, or by design?

Thank you.