[jQuery] get height from hidden element

[David]

Hi,

my problem is, when I try to get the height or any other graphic
property of an element which is hidden (in my case, hidden in one
jQuery UI tab), I can't manage to get the height of the element. If I
do:

$("#my_element").outerHeight()

I get zero. Whereas If I do the same when the element is visible, I
get its height.

I work with jQuery 1.3.2 and FF 3.5.

What am I doing wrong?

Thanks!