mu4e missing chars

[Luca Ferrari]

Hi all,
I suspect this has something to do with font faces, however when I
start mu4e on emacs 27.2, I cannot see the quick jump keys: they are
replaced with an asterisk, so that the whole screen is as follows:

* mu4e - mu for emacs version 0.9.9.5 C

  Basics

        * [*]ump to some maildir
        * enter a [*]earch query
        * [*]ompose a new message

  Bookmarks

        * [* ] Unread messages
        * [* ] Today's messages
        * [* ] Last 7 days
        * [* ] Messages with images


You can see, for example, that the first entry is "[*]ump to some
maildir" instead of "[j]ump to some maildir".
Anyone has a suggestion?

Thanks,
Luca