Refering to CSS elements

Hi,
 
I'm using a seperate CSS file for the styling of all my SVG elements, such
as 
 
polygon.foo
{
    fill: red;
}
 
<polygon class="foo" ....
 
I've noticed that it seems to be case sensitive, i.e. if the class is "Foo",
it doesn't find the CSS element. Is this correct?
 
Thanks
 
Phil