checking for new mail closes the article buffer

[harven]

In a configuration where I both have the summary and article buffer displayed,
when I check for new mail in the summary buffer (M-g gnus-summary-rescan-group)
the *Article* window gets closed. Is there a way to prevent that ?

I tried wraping the scan into a save-window-excursion 

(defun my-scan ()
  (interactive)
  (save-window-excursion
     (gnus-summary-rescan-group)))

The article buffer stays open but its body disappears mysteriously.