[Vala] Vapi generation problem

[Nicolas <c r n a wanadoo fr>]

Hello,

I try to use a non glib-library, and i have a problem generating the 
vapi file.

On my header i have:
typedef struct my_instance my_instance;

In my vapi file, i wrote:
public struct my_instance {}

When i use this structure (test_instance), vala generate this:
my_instance test_instance;

But i need this:
my_instance *test_instance;

There is a way to say to vala to generate the second one ?
Thanks in advance,
Nicolas.