Couchbase Retrieved Document Expiry always set to 0

It seems like the document expiry value is always retrieved as "0" by the couchbase client, although obviously it is taken into account. Any ideas ? (Using couchbase Java Client 2.2.8)

bucket.upsert(JsonDocument.create(key, 5, content));

    try {
        for (int i = 0; i < 10; i++) {
            Thread.sleep(1000);             
            print("expiry :" + bucket.get(key).expiry());
        }
    } catch (NullPointerException e) {
        print("Document Expired");
    }

Code Output :

expiry :0
expiry :0
expiry :0
expiry :0
expiry :0
Document Expired