SDL gfx ZoomSurface

Hi ,

I use zoomSurface() from SDL_gfx library and I’ve this statement:

SDL_Surface *sprite;
sprite = zoomSurface(sprite, zoom, zoom, SMOOTH);

The sprite surface has an alpha channel set to SDL_SRCALPHA.
After the zoom I’ve no more alpha in the sprite surface.

How can I fix this?

Thanks
Alessandro