How to change the UML line width attribute ?

[Maxime Lecoq <maxime lecoq a wanadoo fr>]

Hi,

I'm using Dia for making UML diagrams. I did success in changing the 
line width of an UML class : double click on it (it opens its properties 
window), go to the style panel and change the line width attribute 
(still wrote in english in my french version by the way). This works 
good. Now, I would like to do the same thing with line beetween 2 
classes (inheritance, implementation...). When I double click on a line 
(or do a right click and select properties), there is no line width 
attribute... How could I do ?

Thanks,
--ml.