Scrapy exports invalid json

Scrapy exports invalid json

My parse looks like this:
def parse(self, response):
hxs = HtmlXPathSelector(response)
titles = hxs.select("//tr/td")
items = []
for titles in titles:
item = MyItem()
item['title'] = titles.select('h3/a/text()').extract()
items.append(item)
return items
Why does it output json like this:
[{"title": ["random title #1"]},
{"title": ["random title #2"]}]