gdk_draw_image() not working?

[Tomasz Sterna <tomek xiaoka com>]

I am using the following code (stripped):

---- 8< ----
drawing = gtk_drawing_area_new ();
gc = gdk_gc_new (drawing->window);
image = gdk_image_new (GDK_IMAGE_FASTEST,
                       gdk_visual_get_system(), w, h );
paint_image (image->mem); // custom painting function
gdk_draw_image (drawing->window, gc,
                image, 0, 0, 0, 0, -1, -1 );
---- 8< ----

and I don't see my image on screen :-(

If I replace GdkImage with GdkPixbuf + gdk_draw_pixbuf() I can see my
picture fine.
I already have 16bpp painted picture, so I don't like GdkPixbuf because
I need to convert 16->24bpp (and then GDK converts back, because my
visual is 16bpp).

Is there something wrong with the way I use GtkImage?