Firefox white space between <object> and referenced SVG

Hi,

I am still struggling with getting reliable design with
SVG elements, and the issue I have is that:

1. when I load external SVG with <object>
2. set <object> style "border: 1px solid black"
3. and I use Firefox

There is a thin white space between my SVG
image and <object> border.

The image is still this 10x10 box:

    <svg xmlns="http://www.w3.org/2000/svg">
      <rect width="10" height="10"/>
    </svg>

In Chrome there is no space, and I don't have IE 11
to test. So, there are questions:

1. Where does this white space come from?
2. Is there a specification that tell if it should it be
there or not?
3. Are there any official w3.org render tests that
track such issues (I may be able to add mine)?

-- 
anatoly t.