Unable to create subscribe query

Until now I used the default database adapter for ShareDB, but since I want to support persistent storage, I decided to use this adapter. Only there seems to be a problem when calling connection.createSubscribeQuery(...):

TypeError: Cannot read property '$query' of undefined
    at DB.ShareDbMongo.checkQuery (node_modules\sharedb-mongo\index.js:853:12)
    at DB.ShareDbMongo._getSafeParsedQuery (node_modules\sharedb-mongo\index.js:939:18)
    at DB.ShareDbMongo._query (node_modules\sharedb-mongo\index.js:625:21)
    at node_modules\sharedb-mongo\index.js:686:10
    at node_modules\sharedb-mongo\index.js:74:12
    at DB.ShareDbMongo.getDbs (node_modules\sharedb-mongo\index.js:109:26)
    at DB.ShareDbMongo.getCollection (node_modules\sharedb-mongo\index.js:71:8)
    at DB.ShareDbMongo.query (node_modules\sharedb-mongo\index.js:683:8)
    at Backend._query (node_modules\sharedb\lib\backend.js:495:14)
    at node_modules\sharedb\lib\backend.js:452:15

This is the code which creates the ShareDB backend:

var ShareDB = require('sharedb');
var ShareDBMongo = require('sharedb-mongo');
var sharedb = new ShareDB({db: ShareDBMongo('mongodb://localhost:27017')});
var connection = sharedb.connect();

Everything used to run correctly before (without providing the option, i.e. just using new ShareDB()).

Reproduce the failure using the shown ShareDB and sharedb-mongo setup, starting at connection.createSubscribeQuery and the sharedb-mongo checkQuery stack trace. Trace why the query argument is undefined, then verify that createSubscribeQuery works with the MongoDB adapter without the TypeError.