You can't have the same stylesheet referenced twice

I have conditional stylesheets for IE6 and IE7.

Otherwise I use style.css for all the rest. But I don't want to load the main stylesheet for IE6 & 7 so my set-up was this:

stylesheets-conditional[IE 6][all][] = styleie6.css
stylesheets-conditional[IE 7][all][] = styleie7.css

stylesheets-conditional[!IE][all][] = style.css

Only this means the style.css doesn't load in IE8.

So I tried adding:

stylesheets-conditional[gte IE 7][all][] = style.css

But this won't work because I'm calling the same style sheet. You can work around it by copying and renaming your main stylesheet but it means I spent a good hour wondering why the conditional HTML wasn't even appearing. Either this should be allowed or there should be some sort of notification for the user to explain to them what is going on.