[scribus] White versus transparent pixels question

[Marco]

I'm a new and really happy user of Scribus. It works like a charm with a
few hours of self-learning, supported by the nice on-line documentation.

I have just a problem I can't solve with a document containing an image
having a white object on a transparent background (and some yellow text).
As the final result of my work has to printed on not-white paper all the
white pixels of this image will have to be in the output (printer or ps
file).
Currently the white pixels are discarded, I can see this in the preview
of the print menu with the transparency option enabled, as the white
pixels are shown as they would be transparent. By changing the white
pixels to any other color this problem disappears.
Can anyone please be so kind as telling me how I can have also the white
pixels explicitly in my output? It is maybe trivial, but I could not
find the appropriate switch....

Tnx in advance for your help.

Marco