No no, don't do this, then it will close with </audio autoplay> which is not what you want, there are no HTML tags with two words. TAG.audio(_autoplay='autoplay') is ok and will work. Autoplay is an attribute, the reason you can use it without a value is because HTML allows attribute minimization. If the value there annoys you, you can use XML('<audio autoplay></audio>'), or just don't use a helper.