Javascript – mailto link (in chrome) is triggering window.onbeforeunload – can i prevent this

Possibly related to How to open mailto link in Chrome with Window.open without creating a new tab?

Hi all. I have a form page where i've put a window.onbeforeunload confirm, to stop people navigating away and losing their changes by accident:

window.onbeforeunload = function(){
  if(changed)
    return "You have unsaved changes.  Do you really want to leave this page without saving?";
};  

where changed is a variable i set to true whenever the user makes any changes. That's all fine. However, i've also added some mailto links to the page, like so:

<a class="button button-alt" href="mailto:foo@foo.com">Report a problem</a>

Even though the mailto isn't navigating away from the page (it's opening the users default mail app), it's still triggering the onbeforeunload event, prompting the confirm box, which is annoying. I can get round it setting target="_blank" on the link, but then the user is left sitting in an empty tab.

Can i set the mailto link to not trigger the onbeforeunload event? I thought of a horribly hacky way of doing it by having another temporary javascript variable which causes the onbeforeunload confirm to not trigger, but it seems kind of dirty. I'll do it anyway while i wait for a response but does anyone have a nicer solution?

thanks, max