Diagonal title in a mask (Impress 5.2.3.2)

Hi all,

I would like to write a diagonal title (5-degrees rotation in the text box) in a mask. No problem with that when i edit the mask, the title text appears as i want.
But, as soon as I apply the mask to all the slides, the text appears horizontally

Thanks in advance for any tips or help…
Regards,
Tarto