[6.9.3] serializeDate does not work properly with arrayFormat #364

qs.stringify({ a: [new Date()] }, { serializeDate: function (d) { return d.getTime(); }, arrayFormat: 'comma' })

should yield: a=<timestamp>
but yields: a=Fri%20May%2001%202020%2019%3A54%3A33%20GMT%2B0530%20%28India%20Standard%20Time%29

It works when I remove arrayFormat.