Using Swagger when returning JsonNode

Question

I've currently written a Spring Boot application that returns a Response Object (a class I created) on one of it's REST calls. It was working fine, until I incorporated Swagger and now gives me the following error:

<Response>
    <timeTook>69</timeTook>
    <hitsCount>138</hitsCount>
    <hits>
        <hits>
            <msg>
                <Map>
                    <timestamp>1539357450970</timestamp>
                    <status>200</status>
                    <error>OK</error>
                    <message>Could not write JSON: Invalid white space character (0x1) in text to output (in xml 1.1, could output as a character entity); nested exception is com.fasterxml.jackson.core.JsonGenerationException: Invalid white space character (0x1) in text to output (in xml 1.1, could output as a character entity)</message>
                    <path>/api/messagesearch/1.0/search</path>
                </Map>

Here is my Response class that I use to create the Response object.

public class Response {

    private String timeTook;
    private String hitsCount;
    private List<JsonNode> hits;

    public Response(String took, String hitsCount, List<JsonNode> hits){
        this.timeTook = took;
        this.hitsCount = hitsCount;
        this.hits = hits;
    }

    public String getTimeTook() {
        return timeTook;
    }

    public String getHitsCount() {
        return hitsCount;
    }

    public void setHitsCount(String hitCount) {
        this.hitsCount = hitCount;
    }

    public void setTimeTook(String timeTook) {
        this.timeTook = timeTook;
    }

    public List<JsonNode> getHits() {
        return hits;
    }

    public void setHits(List<JsonNode> hits) {
        this.hits = hits;
    }
}

It seems to me that Swagger does not particularly like the use of JsonNodes. It shows the timetook and hitCount strings. Anyone know how to work around this? Thanks.