MongoDB (Node.js Native driver) large gridfs upload fails

Mongodb seems to be arbitrarily returning early when I try to upload a large file (1.8GB) to GridFS. Smaller files work just fine.

I'm using the node.js native driver. The code (with a few things omitted for brevity) is as follows:

var objectId = new ObjectID(),
gridStore = new GridStore(db, objectId, filename /*declared elsewhere*/, "w", { "content_type": contentType /* declared elsewhere */ }), 
obj = {};

gridStore.open(function (err, gs) {
    console.log("gridStore open");
    gs.writeFile(tempFile, function (err, doc) {
        if (err) {
            throw err;
        }

        console.log("file written");
            obj.fileId = doc._id;

        // double check the md5 of the uploaded file against what was uploaded
                // (md5 variable declared elsewhere)
        if (doc.md5 !== md5) {
            console.log(doc);
            console.log(doc.md5);
            console.log(md5);
            //delete bad file
            GridStore.unlink(db, doc.filename, function (err, gridStore) {
                if (err) {
                    throw err;
                }
            });

        } else {
            // do the desired stuff
        }
    });
});

The "doc" object always seems to return with a different length (and obviously a different md5).