line-breaks after slashes in filenames

Hi,

I'm using docbook - xsl-fo and fop to create a pdf. In my text I have
occasionally the problem, that a part marked with <filename> breaks
inappropriate like this:

some long and random text /
etc/passwd some more text

This is not what I want, of course. I want to get the '/' on the next
line. Its ok to break after a slash on longer filenames, but not after
the first.

I tried to force a line-break by using a processing instruction to
insert a <fo:block/> element in my FO, but this breaks the justification
of the previous line, which also doesn't look pretty good.

How can I solve this problem? A solution that would allow forced
line-breaks without breaking the justification would be ok for me.


Bjoern