JSON-LD serialization string without indentation, spaces or line breaks in RDF4J / Sesame

I am trying to serialize a Model as JSON-LD and store it in a string variable using RDF4J.

My code looks like this:

public void storeAsString(Model model) {
    StringWriter stringWriter = new StringWriter();
    RDFWriter rdfWriter = Rio.createWriter(RDFFormat.JSONLD, stringWriter);

    rdfWriter.getWriterConfig().set(JSONLDSettings.JSONLD_MODE, JSONLDMode.COMPACT);
    rdfWriter.getWriterConfig().set(JSONLDSettings.OPTIMIZE, true);

    Rio.write(model, rdfWriter);
    String output = stringWriter.toString();
}

It gives me a JSON-LD string, but without any indentation, spaces or line breaks such that System.out.println(output) is not human-readable. It looks like this:

{"@context":"http://schema.org/","type":"Person","jobTitle":"Professor","name":"Jane Doe","telephone":"(425) 123-4567","url":"http://www.janedoe.com"}

In Apache Jena there is an RDFFormat called JSONLD_PRETTY which would give me the desired output format. It looks similar to this:

{
  "@context": "http://schema.org/",
  "@graph": [
    {
      "id": "_:b0",
      "type": "Person",
      "jobTitle": "Professor",
      "name": "Jane Doe",
      "telephone": "(425) 123-4567",
      "url": "http://www.janedoe.com"
    }
  ]
}

Is this also possible with Eclipse RDF4J?

Thank you in advance!

Edit: When I am trying to store the JSON-LD string with MongoDB it throws this error: Invalid BSON field name. Is this an issue with the serialization or with my built model?

Edit No. 2: The above code works flawlessy with the Turtle format, for example. I am having this problem just with JSON-LD and RDFJSON.

This is possible, by setting the BasicWriterSettings.PRETTY_PRINT option to true:

rdfWriter.getWriterConfig().set(BasicWriterSettings.PRETTY_PRINT, true);

No idea about the MongoDB issue, sounds like it should be a separate question.