amphtml url incorrect

Hello —
I have installed your plugin and noticed right away that you are displaying amp page by appending ?amp to the end of the URL, however the meta link on the original page doesn’t point to ?amp, instead it points to non-existing /amp/ URL.

<link rel=”amphtml” href=”http://www.website.com/subpage/amp/”/&gt;

Should it be this instead?
<link rel=”amphtml” href=”http://www.website.com/subpage/?amp”/&gt;

Otherwise the plugin looks great!